By the 1952 season, the university decided to deemphasize sports. The new president at Louisville, Dr. Phillip Davidson, reduced the amount of athletic aid, and tightened academic standards for athletes. As a result, 15 returning players could not meet the new standards and lost their scholarships.
In 1952 Coach Camp switched the team to one-platoon football. Unitas played safety or linebacker on defense, quarterback on offense, and kick/punt returner on special teams. The Cards won their first game against Wayne State, and destroyed Florida State 41-14 in the second game. Unitas completed 16 of 21 passes for 198 yards and three touchdowns. It was said that Unitas put on such a show at the Florida State game that he threw a pass under his legs for 15 yards. The rest of the season was a struggle for the Cards, who finished 3-5. Unitas completed 106 of 198 passes for 1,540 yards and 12 touchdowns in his sophomore year.
The team won their first game in 1953, against Murray State, and lost the rest for a record of 1-7. One of the most memorable games of the season came in a 59-6 loss against Tennessee. Unitas completed 9 of 19 passes for 73 yards, rushed 9 times for 52 yards, returned 6 kickoffs for eighty-five yards, 1 punt for three yards, and had 86 percent of the team's tackles. The only touchdown the team scored was in the fourth quarter when Unitas made a fake pitch to the running back and ran the ball 23 yards for a touchdown. Unitas was hurt later in the fourth quarter while trying to run the ball, and on his way off the field received a standing ovation. When he got to the locker room he was so worn that his jersey and shoulder pads had to be cut off, because he could not lift his arms. Louisville ended the season with 20-13 loss to Eastern Kentucky in which Unitas was intercepted twice by Roy Kidd. In his junior year, Unitas completed 49 of 95 passes for 470 yards and three touchdowns.
Unitas was elected captain for the 1954 season, but due to an early injury did not see much playing time. His first start of the season was the third game against Florida State. Of the 34-man team, 21 were freshmen. The 1954 Louisville Cardinals went 3-6, with the last win at home against Morehead State. Unitas was slowed by so many injuries his senior year that he did not lead the team in passing yards. He threw for 527 yards, second to Jim Houser’s 560.
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 steel worker much like Unitas, at the latter's scheduled Colts tryout. They borrowed money from friends to pay for the gas to make the trip. Deglau, a semi-pro player and family friend, told a reporter after Unitas' 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 rejected Steeler quarterback.
When starting quarterback George Shaw suffered a broken leg against the Chicago Bears in the season's fourth game, Unitas made a nervous debut. His first 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 was named the NFL's Most Valuable Player by the Newspaper Enterprise Association (NEA).
The Colts won the NFL championship under Unitas' leadership in 1958, by defeating the New York Giants 23-17 in sudden death overtime. 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) and UPI for the first time, leading the NFL in passing yards (2,899), touchdown passes (32) and completions (193).Unitas then led the Colts to a repeat championship, beating the Giants again 31-16 in the title game.
As the 1950s turned into the 1960s, the Colts fortunes (and win totals) declined. Injuries to key players such as Alan Ameche, Raymond Berry and Lenny Moore were a contributing factor to this. Unitas' streak of 47 straight games with at least one touchdown pass ended against the Los Angeles Rams in week 11 of the 1960 season. After three middle-of-the-pack seasons, Colts owner Carroll Rosenbloom fired Weeb Ewbank and replaced him with Don Shula, the then-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 3 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. The 1964 season would see the Colts return to the top of the Western Conference. After dropping their season opener to the Vikings, the Colts ran off 10 straight victories and finished the season with a 12-2 record. The season was one of Unitas' 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 would end on a disappointing note for the Colts as they were upset by the Cleveland Browns in the 1964 NFL Championship Game, losing 27-0. More postseason heartbreak would follow in 1965. 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. The season had been another fine one for Unitas, as he threw for 2,530 yards, 23 touchdowns and finished with a league-high 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 it would be running back Tom Matte who filled in as the emergency QB for the regular-season finale and the playoff loss to the Packers. After once again finishing 2nd 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 awards 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. Once again the season ended on a sour note for the Colts, as they were shut out of the newly-instituted four team NFL playoff after losing the divisional tiebreaker to the Rams due to a 34-10 loss to them in the regular season finale.
Unitas missed most of the 1968 season with a chronically sore elbow but the Colts still marched to a league-best 13-1 record behind backup quarterback (and 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 wherein Joe Namath guaranteed a New York Jets win despite conventional wisdom. Unitas' insertion was a desperation move in an attempt to retrieve dominance of the NFL over the upstart AFL. Unitas helped put together the Colts' only score, a touchdown late in the game. Despite not playing until the fourth quarter, Unitas still finished with more passing yards than the team's starter, Morrall. In 1970, Unitas led the Colts to Super Bowl V. He was knocked out of the game in the second quarter, after throwing a 75-yard touchdown pass (setting a then-Super Bowl record) that helped lift the team to victory. In 1971 Unitas brought the Colts to the AFC Championship game and lost to Miami 21-0.
Unitas was involved in only one other head-to-head meeting with Namath after their 1970 regular season meeting (won by the Colts, 29-22, on a day when Namath's wrist was broken on the final play of the game). That last meeting was a memorable one. On September 24, 1972, at Memorial Stadium, Unitas 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.
Unitas was traded to the San Diego Chargers in 1973, and retired from football in 1974. He finished his 17 NFL seasons with 2,830 completions in 5,186 passes for 40,239 yards and 290 touchdowns, with 253 interceptions. He also rushed for 1,777 yards and 13 touchdowns.
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 16-game seasons). His 47-game touchdown streak between 1956 and 1960 is a record that still stands and is considered by many the Mount Everest-like football equivalent to Joe DiMaggio's 56-game baseball hitting streak.
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, Brooks Robinson, Cal Ripken Jr., Ray Lewis, and Michael Phelps are generally considered the city's foremost sports icons. After Robert Irsay moved the Colts franchise to Indianapolis, in 1984, a move reviled to this day in Baltimore as "Bob Irsay's Midnight Ride," Unitas was so outraged that he cut all ties to the relocated team (though his #19 jersey is still retired by the Colts). Other prominent old-time Colts followed his lead. He 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; it is now on display in the Sports Museum at Camden Yards.
Unitas actively lobbied for another NFL team to come to Baltimore. After the NFL returned to Baltimore as the Ravens for the 1996 season, Unitas and most of the other old-time Colts regarded the Ravens as the true successors of the Baltimore Colts. Unitas was frequently seen on the Ravens' sidelines at home games and received a thunderous ovation every time he was pictured on each of the huge widescreen SACO SmartVision boards 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."
In December 2005, the state of Indiana attempted to raise funds for a new football stadium by issuing a Colts specialty license plate and auctioning off plates whose registrations represented distinctive Colts position-number pairings (e.g. "QB 18" for Peyton Manning). When the state offered Unitas's "QB 19" for bid, the Unitas family sued, eventually getting the offer revoked and receiving an out-of-court settlement.
Toward the end of his life, Unitas brought media attention to the many permanent physical disabilities that he and his fellow players suffered during the early years of football, before padding and other safety features designed to prevent such injuries had been invented. Unitas himself lost almost total use of his right hand, which had become mangled by the end of his playing career, with the middle finger and thumb noticeably disfigured from being repeatedly broken.