Mack enrolled at the University of Michigan in 1962 and played college football for Michigan Wolverines football teams from 1963 to 1965. As a sophomore in 1963, he played at the end position and spent most of the season on the bench. After the 1963 season, Mack switched to the tackle position at the suggestion of Michigan coach Bump Elliott. Mack later referred to the position change as "the big break of my life," an opportunity that "turned my whole experience in terms of football around." As a junior, he started seven games at right tackle and won the Meyer Morton Award for the 1964 Michigan Wolverines football team that compiled a 9–1 record, outscored opponents 235–83, and defeated Oregon State in the 1965 Rose Bowl. As a senior, he started seven games at right tackle for the 1965 Michigan team, and he was selected by the Associated Press as a first-team tackle on the 1965 All-Big Ten Conference football team. Mack was inducted into the University of Michigan Athletic Hall of Honor in 2006. While attending Michigan, Mack was a member of Sigma Alpha Epsilon fraternity.
Los Angeles Rams
Mack was selected by the Los Angeles Rams in the first round, as the second overall pick, in the 1966 NFL Draft. During Mack's rookie season with the Rams, starter Don Chuy was injured during the fifth game of the season, allowing Mack to move into the lineup. He started nine games during the 1966 season and became a fixture for the Rams at the left guard position for the next 13 seasons. During his NFL career, Mack never missed a game due to injury, appearing in 184 consecutive contests, the third longest streak in Rams history behind Merlin Olsen and Jack Youngblood. During Mack's career with the Rams, the club enjoyed a.720 winning percentage with a won-lost-tie record of 129-48-7, won their division eight times, and reached four NFC championship games. In 1973, the Rams scored led the NFL with 388 points. In 1974, the Rams lost to the Minnesota Vikings by four points in the, with a controversial penalty call against Mack costing the Rams a touchdown. The Rams had the ball at the one-yard line on second down when the Vikings' Alan Page made contact with Mack; the referee called illegal procedure on Mack, but replays showed that Mack had not moved. After the game, Mack insisted he had not moved but credited Page with "a smart play" in making contact since a penalty, if called against the Vikings, would have been meaningless. Mack was selected to 11 Pro Bowls, the first coming after his second season in 1967. He missed only one Pro Bowl appearance the rest of his career. Mack's 11 invitations earned him a third-place tie with Bob Lilly and Ken Houston for the most selections of all time. Mack was selected first-team All-Pro four times and second-team All-Pro four times. In addition he was named All-NFC eight times between 1970 and 1978. Mack announced in late November 1978 that he would retire at the end of the 1978 NFL season. He was inducted into the Pro Football Hall of Fame in 1999.
Later years
After retiring from football, Mack worked as an engineer, using the engineering degree he received at the University of Michigan. He eventually became a lobbyist for Bechtel Group, Inc.
