Following his graduation from Notre Dame, Page was drafted by the Minnesota Vikings, for whom he played from 1967 until 1978. In 1978, Page joined the Chicago Bears, with whom he played through the 1981 season and where he amassed 40 of his career sacks.
While in the NFL, Page earned All-Pro honors six times and made second-team all-league three additional times. He was voted to nine consecutive Pro Bowls. Eleven times he was voted All-Conference, in 1968 and 1969 as All-Western Conference and 1970 through 77 and 1980 as an All- National Football Conference.
In 1971, Page was named both the AP NFL Defensive Player of the Year (the first player to be named such) and the AP's NFL Most Valuable Player. Page was the first defensive player to be named MVP since the award's inception. In addition, he was voted the NEA NFL Defensive Player of the Year in 1973.
Page was National Football League Players Association player representative, 19701974, 19761977, and a member of the NFLPA Association Executive Committee, 1972-1975. Named to the Vikings' 40th Anniversary Team in 2000. Along the way, Page was named the Associated Press NFL Defensive Player of the Week three times: Week 9, 1967; Week 8, 1968; Week 13, 1971. Page was a member of the Vikings famous "Purple People Eaters".
After his playing career he dabbled in the media, first as a color commentator on Turner Broadcasting System covering the College Football Game of the Week series during the Fall of 1982 and then as a commentator on National Public Radio from 1982-83.
In 1988, Page was further honored by his induction into the Pro Football Hall of Fame. In 1999, he was ranked number 34 on The Sporting News' list of the 100 Greatest Football Players, the highest-ranking Viking player. He received the NFL Alumni Career Achievement Award in 1995 for attaining success in his post-NFL career.
Long before Page's football career came to a close, he was laying the groundwork for his future role as a justice with the Minnesota Supreme Court. While still playing for the Vikings, Page attended the University of Minnesota Law School, from which he received his Juris Doctor in 1978. Following graduation, he worked with the law firm of Lindquist and Vennum in Minneapolis from 1979 to 1984 outside the football season. In 1985, Page was appointed Special Assistant Attorney General, and was soon thereafter promoted to Assistant Attorney General.
In 1992, Page was elected to an open seat as an Associate Justice of the Minnesota Supreme Court, becoming the first African-American to ever serve on that court. He was re-elected in 1998, becoming the biggest vote-getter in Minnesota history, and was again re-elected.