After serving with the Marines, Whitlow qualified for the Summer Olympics trials in shot put, but decided to play football instead.[3][1] He signed with the Chicago Bears in 1960, but was then traded to the Washington Redskins.[2] Midway through the 1961 season, he was traded to the Detroit Lions, where he played through 1965 and played every offensive down in 1962 and 1963.[2] Whitlow was then traded to the Atlanta Falcons during their inaugural 1966 season. He was then traded to the Los Angeles Rams for undisclosed draft picks, but never played for the Rams.[4][5] In 1968, he was signed by the Pittsburgh Steelers, but was waived before the end of the offseason.[6] He was then signed by the Cleveland Browns and played for them for one season, but then had to retire after a hernia operation.[7] He attempted to make a comeback in 1974 with the World Football League's Portland Storm, but failed.[8]
During the Lions' 1963 season, Whitlow was the center for George Plimpton when Plimpton was practicing and playing with the team for the Sports Illustrated article that became the book Paper Lion.[9]
A longtime racing fan who idolized Richard Petty and A. J. Foyt, Whitlow became interested in dabbling in a racing career when he was still with the Lions, though the team and his wife forbade him from pursuing it. After retiring from football, he purchased a 1970 Dodge Charger and received a helmet from New Orleans Saints owner John W. Mecom Jr., who previously ran the Mecom Racing Team. He raced with No. 51 as a nod to his number from his playing days.[10]
He explained in July 1973 that "racing and football have some of the same organizations. You've got to have organization to win in either sport. You've got to think about what you're going to do, and you have to be able to analyze what you're doing wrong."[11] Otherwise, he stressed "there is simply no comparison" between the two sports.[10]