Unitas set many NFL records and was named Most Valuable Player three times in 1959, 1964, and 1967, in addition to receiving 10 Pro Bowl and five first-team All-Pro honors. He helped lead the Colts to four championship titles; three in the pre-merger era in 1958, 1959, and 1968, and one in the Super Bowl era in Super Bowl V. His first championship victory is regarded as one of the league's greatest games and credited with helping popularize the NFL. Between 1956 and 1960, he set the record for most consecutive games with a touchdown pass at 47, which held for 52 years.
Nicknamed "Johnny U" and the "Golden Arm", Unitas was considered the prototype of the modern era marquee quarterback. He was inducted into the Pro Football Hall of Fame in 1979.
After his collegiate career, the Pittsburgh Steelers of the NFL drafted Unitas in the ninth round. However, he was released before the season began as the odd man out among four quarterbacks trying to fill three spots. Steelers' head coach Walt Kiesling had made up his mind about Unitas; he thought he was not smart enough to quarterback an NFL team, and he was not given any snaps in practice with the Steelers. Among those edging out Unitas was Ted Marchibroda, future longtime NFL head coach. Out of pro football, Unitas—by this time married—worked in construction in Pittsburgh to support his family. On the weekends, he played quarterback, safety and punter on a local semi-professional team called the Bloomfield Rams for $6 a game.
In 1956, Unitas joined the Baltimore Colts of the NFL under legendary coach Weeb Ewbank, after being asked at the last minute to join Bloomfield Rams lineman Jim Deglau, a Croatian steelworker with a life much like Unitas, at the latter's scheduled Colts tryout. The pair borrowed money from friends to pay for the gas to make the trip. Deglau later told a reporter after Unitas's death, "[His] uncle told him not to come. [He] was worried that if he came down and the Colts passed on him, it would look bad (to other NFL teams)." The Colts signed Unitas, much to the chagrin of the Cleveland Browns, who had hoped to claim the former Steeler quarterback.
Unitas made his NFL debut with an inauspicious "mop-up" appearance against Detroit, going 0–2 with one interception. Two weeks later, starting quarterback George Shaw suffered a broken leg against the Chicago Bears. In his first serious action, Unitas's initial pass was intercepted and returned for a touchdown. Then he botched a hand-off on his next play, a fumble recovered by the Bears. Unitas rebounded quickly from that 58–27 loss, leading the Colts to an upset of Green Bay and their first win over Cleveland. He threw nine touchdown passes that year, including one in the season finale that started his record 47-game streak. His 55.6-percent completion mark was a rookie record.
In 1957, his first season as the Colts full-time starter at quarterback, Unitas finished first in the NFL in passing yards (2,550) and touchdown passes (24) as he helped lead the Colts to a 7–5 record, the first winning record in franchise history. At season's end, Unitas received the Jim Thorpe Trophy as the NFL's Most Valuable Player by the Newspaper Enterprise Association (NEA).
Unitas continued his prowess in 1958 passing for 2,007 yards and 19 touchdowns as the Colts won the Western Conference title. The Colts won the NFL championship under his leadership on December 28, 1958, by defeating the New York Giants 23–17 in sudden death overtime on a touchdown by fullback Alan Ameche. It was the first overtime game in NFL history, and is often referred to as the "greatest game ever played". The game, nationally televised by NBC, has been credited for sparking the rise in popularity of professional football during the 1960s.
In 1959, Unitas was named the NFL's MVP by the Associated Press (AP) for the first time, as well as United Press International's player of the year, after leading the NFL in passing yards (2,899), touchdown passes (32), and completions (193). He then led the Colts to a repeat championship, beating the Giants again 31–16 in the title game.
As the 1960s began, the Colts' fortunes (and win totals) declined. Injuries to key players such as Alan Ameche, Raymond Berry, and Lenny Moore were a contributing factor. Unitas's streak of 47 straight games with at least one touchdown pass ended against the Los Angeles Rams in week 11 of the 1960 season. In spite of this, he topped the 3,000-yard passing mark for the first time and led the league in touchdown passes for the fourth consecutive season.
After three middle-of-the-pack seasons, Colts owner Carroll Rosenbloom fired Weeb Ewbank and replaced him with Don Shula, who at the time was the youngest head coach in NFL history (33 years of age when he was hired). The Colts finished 8–6 in Shula's first season at the helm, good enough for only third place in the NFL's Western Conference, but they did end the season on a strong note by winning their final three games. The season was very successful for Unitas personally, as he led the NFL in passing yards with a career-best total of 3,481 and also led in completions with 237.
In the 1964 season the Colts returned to the top of the Western Conference. After dropping their season opener to the Minnesota Vikings, the Colts ran off 10 straight victories to finish with a 12–2 record. The season was one of Unitas's best as he finished with 2,824 yards passing, a league-best 9.26 yards per pass attempt, 19 touchdown passes and only 6 interceptions. He was named the NFL's Most Valuable Player by the AP and UPI for a second time. However, the season ended on a disappointing note for the Colts as they were upset by the Cleveland Browns in the 1964 NFL Championship Game, losing 27–0.
Unitas resumed his torrid passing in 1965, throwing for 2,530 yards, 23 touchdowns and finishing with a league-high and career-best 97.1 passer rating. But he was lost for the balance of the season due to a knee injury in a week 12 loss to the Bears. Backup quarterback Gary Cuozzo also suffered a season-ending injury the following week, and running back Tom Matte filled in as the emergency quarterback for the regular season finale and in a playoff loss to the Packers. The Colts and Packers finished in a tie for first place in the Western Conference and a one-game playoff was played in Green Bay to decide who would be the conference representative in the 1965 NFL Championship Game. The Colts lost in overtime 13–10 due in large part to a game-tying field goal by Don Chandler that many say was incorrectly ruled good.
Unitas, healthy once more, threw for 2,748 yards and 22 touchdowns in 1966 in a return to Pro Bowl form. However, he posted a league-high 24 interceptions.
After once again finishing second in the Western Conference in 1966, the Colts rebounded to finish 11–1–2 in 1967 tying the Los Angeles Rams for the NFL's best record. In winning his third MVP award from the AP and UPI in 1967 (and his second from the NEA), Unitas had a league-high 58.5 completion percentage and passed for 3,428 yards and 20 touchdowns. He openly complained about having tennis elbow and he threw eight interceptions and only three touchdown passes in the final five games. Once again, the season ended in loss for the Colts, as they were shut out of the newly instituted four-team NFL playoff after losing the divisional tiebreaker to the Rams, a 34–10 rout in the regular season finale.
In the final game of the 1968 preseason, the muscles in Unitas's arm were torn when he was hit by a member of the Dallas Cowboys defense. Unitas wrote in his autobiography that he felt his arm was initially injured by the use of the "night ball" that the NFL was testing for better TV visibility during night games. In a post-game interview the previous year, he noted having constant pain in his elbow for several years prior. He would spend most of the season sitting on the bench. The Colts still marched to a league-best 13–1 record behind backup quarterback and ultimate 1968 NFL MVP Earl Morrall. Although he was injured through most of the season, Unitas came off the bench to play in Super Bowl III, the famous game where Joe Namath guaranteed a New York Jets win despite conventional wisdom. Unitas's insertion was a desperation move in an attempt to retrieve dominance of the NFL over the upstart AFL. Although the Colts won an NFL Championship in 1968, they lost the Super Bowl to the AFL Champion New York Jets, thus becoming the first-ever NFL champions that were not also deemed world champions. Unitas helped put together the Colts' only score, a touchdown late in the game. Unitas also drove the Colts into scoring position following the touchdown and successful onside kick, but head coach Don Shula eschewed a field goal attempt, which (if successful) would have cut the Jets' lead to 16–10. Despite not playing until late in the third quarter, he still finished the game with more passing yards than the team's starter, Earl Morrall.
After an off-season of rehabilitation on his elbow, Unitas rebounded in 1969, passing for 2,342 yards and 12 touchdowns with 20 interceptions. But the Colts finished with a disappointing 8–5–1 record, and missed the playoffs.
In 1970, the NFL and AFL had merged into one league, and the Colts moved to the new American Football Conference, along with the Cleveland Browns and the Pittsburgh Steelers. He threw for 2,213 yards and 14 touchdowns while leading the Colts to an 11–2–1 season. In their first rematch with the Jets, Unitas and Namath threw a combined nine interceptions in a 29–22 Colts win. Namath threw 62 passes and broke his hand on the final play of the game, ending his season.
Unitas threw for 390 yards, three touchdowns, and no interceptions in AFC playoff victories over the Cincinnati Bengals and the Oakland Raiders. In Super Bowl V against the Dallas Cowboys, he was knocked out of the game with a rib injury in the second quarter, soon after throwing a 75-yard touchdown pass (setting a then-Super Bowl record) to John Mackey. However, he had also tossed two interceptions before his departure from the game. Earl Morrall came in to lead the team to a last-second, 16–13 victory.
In 1971, Unitas split playing time with Morrall, throwing only three touchdown passes. He started both playoff games, a win over the Cleveland Browns that sent the Colts to the AFC Championship game against the Miami Dolphins, which they lost by a score of 21–0. Unitas threw three interceptions in the game, one of which was returned for a touchdown by safety Dick Anderson.
The 1972 season saw the Colts declining. After losing the season opener, Unitas was involved in the second and final regular season head-to-head meeting with "Broadway" Joe Namath. The first was in 1970 (won by the Colts, 29–22). The last meeting took place on September 24, 1972 at Memorial Stadium. He threw for 376 yards and three touchdowns, but Namath upstaged him again, bombing the Colts for 496 yards and six touchdowns in a 44–34 Jets victory – their first over Baltimore since the 1970 merger. After losing four of their first five games, the Colts fired head coach Don McCafferty, and benched Unitas.
One of the more memorable moments in football history came on Unitas's last game in a Colts uniform at Memorial Stadium, in a game against the Buffalo Bills. He was not the starter for this game, but the Colts were blowing the Bills out by a score of 28–0 behind Marty Domres; Unitas entered the game due to the fans chanting, "We want Unitas!!!", and a plan devised by head coach John Sandusky to convince Unitas that the starting quarterback was injured. Unitas came onto the field, and threw two passes, one of which was a long touchdown to wide receiver Eddie Hinton which would be his last pass as a Colt. The Colts won the game by the score of 35–7.
Unitas was traded from the Colts to the San Diego Chargers on January 20, 1973, in a transaction that originally had future considerations returning to Baltimore. The deal's only obstacle was the personal services contract he had signed with the Colts in 1970 which would've kept him employed within the organization on an annual salary of $30,000 over ten years once his career as an active player ended. The pact had been signed when the ballclub was owned by Carroll Rosenbloom who subsequently acquired the Los Angeles Rams on July 13, 1972, in a franchise swap with Robert Irsay. The deal was completed when the Chargers purchased that contract. Eager to sever all ties with the Colts, Unitas signed a new two-year contract with the Chargers on June 8, 1973. He succeeded John Hadl who had requested and was granted a trade to the Rams.
Unitas started the season with a 38–0 loss to the Washington Redskins. He threw for just 55 yards and 3 interceptions, and was sacked 8 times. His final victory as a starter came against the Buffalo Bills in week two. Unitas was 10–18 for 175 yards, two touchdown passes, and no interceptions in a 34–7 Chargers rout. After a loss to the Bengals in week three, many were questioning Unitas' role as a starter. Two weeks later, he threw two first-half interceptions, passed for only 19 yards, and went 2-for-9 against the Pittsburgh Steelers. He was then replaced by rookie quarterback, future Hall of Famer Dan Fouts. After having posted a 1–3 record as a starter, Unitas retired in the preseason of 1974.
Unitas finished his 18 NFL seasons with 2,830 completions in 5,186 attempts for 40,239 yards and 290 touchdowns, with 253 interceptions. He also rushed for 1,777 yards and 13 touchdowns. Plagued by arm trouble in his later seasons, he threw more interceptions (64) than touchdowns (38) in 1968–1973. After averaging 215.8 yards per game in his first 12 seasons, his production fell to 124.4 in his final six. His passer rating plummeted from 82.9 to 60.4 for the same periods. Even so, Unitas set many passing records during his career. He was the first quarterback to throw for more than 40,000 yards, despite playing during an era when NFL teams played shorter seasons of 12 or 14 games (as opposed to today's 17-game seasons) and prior to modern passing-friendly rules implemented in 1978. His 32 touchdown passes in 1959 were a record at the time, making Unitas the first quarterback to hit the 30 touchdown mark in a season. His 47-game consecutive touchdown streak between 1956 and 1960 was a record considered by many to be unbreakable. The streak stood for 52 years before being broken by New Orleans Saints quarterback Drew Brees in a game against the San Diego Chargers on October 7, 2012.
After his playing days were finished, Unitas settled in Baltimore where he raised his family while also pursuing a career in broadcasting, doing color commentary for NFL games on CBS in the 1970s. He was elected to the Pro Football Hall of Fame in 1979. After Robert Irsay moved the Colts franchise to Indianapolis in 1984, a move known to this day in Baltimore as "Bob Irsay's Midnight Ride," he was so outraged that he cut all ties to the relocated team (though his No. 19 jersey is still retired by the Colts), declaring himself strictly a Baltimore Colt for the remainder of his life. Some other prominent old-time Colts followed his lead, although many attended the 1975 team's reunion at Lucas Oil Stadium in Indianapolis in 2009. A total of 39 Colts players from that 1975 team attended said reunion in Indianapolis, including Bert Jones and Lydell Mitchell. Unitas asked the Pro Football Hall of Fame on numerous occasions (including on Roy Firestone's Up Close) to remove his display unless it was listed as belonging to the Baltimore Colts. The Hall of Fame has never complied with the request. Unitas donated his Colts memorabilia to the Babe Ruth Museum in Baltimore; they are now on display in the Sports Legends Museum at Camden Yards.
Unitas was inducted into the American Football Association's Semi Pro Football Hall of Fame in 1987.
Unitas actively lobbied for another NFL team to come to Baltimore. After the Cleveland Browns moved to Baltimore in 1996 and changed their name to the Ravens, he and some of the other old-time Colts attended the Ravens' first game ever against the Raiders on Opening Day at Memorial Stadium. He was frequently seen on the Ravens' sidelines at home games (most prominently in 1998 when the now-Indianapolis Colts played the Ravens in Baltimore) and received a thunderous ovation every time he was pictured on each of the huge widescreens at M&T Bank Stadium. He was often seen on the 30-yard line on the Ravens side. When the NFL celebrated its first 50 years, Unitas was voted the league's best player. Retired Bears quarterback Sid Luckman said of Unitas, "He was better than me, better than Sammy Baugh, better than anyone."
Unitas lived most of the final years of his life severely hobbled. Due to an elbow injury suffered during his playing career, he had only very limited use of his right hand, and could not perform any physical activity more strenuous than golf due to his artificial knees.
In 1991, Unitas and his wife filed for bankruptcy protection under Chapter 11. Their court filings showed that the couple owed creditors as much as $3.2 million but had assets of about $1.4 million. His financial problems arose in part from a business venture in which he and two partners took out loans to buy National Circuits Inc., a maker of printed circuit boards, and the firm subsequently failed.