Haley was a starter for the James Madison Dukes during his entire college career (1982-1985). He was a two-time All-American and finished his career as the school's leading tackler with 506 stops. Haley is a member of Alpha Phi Alpha fraternity, having entered the fraternity through the Xi Delta Chapter at James Madison University.
Haley has the distinction of being the only player in NFL history to have been on five Super Bowl-winning teams. In 1986 Haley was voted All-Rookie by Pro Football Weekly and United Press International and led all rookies with 12 sacks. The following year he again played a designated pass rusher role, coming into the game in likely passing situations. In 1988 he became a starter at left outside linebacker for the 49ers and held that spot through 1991. As he had in his first two seasons Haley was a pass rusher in passing situations for the 49ers. In 1990 Haley was voted the NFC Defensive Player of the Year by UPI and was a consensus All-Pro. While playing for the San Francisco 49ers from 1986–1991, he won rings from Super Bowl XXIII and Super Bowl XXIV following the 1988 and 1989 seasons, respectively. After having a personal conflict with 49ers head coach George Seifert and a physical confrontation with quarterbackSteve Young, Haley was traded to the Dallas Cowboys in the 1992 off-season, with whom he won three more Super Bowl rings over the next four seasons in 1992 (XXVII), 1993 (XXVIII), and 1995 (XXX).
With the Cowboys Haley won his second NFC Defensive Player of the Year Award by UPI and was a consensus All-Pro once again. He won this playing right defensive end in the Cowboys 4-3 defense. Although injuries would eventually force his retirement in 1996, Haley briefly resurfaced for the 1998 playoffs to aid the 49ers, and played for them in 1999. Finally out of playing football permanently, Haley turned to assistant coaching, and was a defensive assistant for the Detroit Lions.
In his 12 NFL seasons, Haley recorded 100.5 quarterback sacks, two interceptions (nine return yards), and eight fumble recoveries, which he returned for nine yards and a touchdown. He was also selected to play in five Pro Bowls (1988, 1990, 1991, 1994, 1995) and was named NFL All-Pro in 1990 and 1994.
Haley's supporters, who included the late Bill Walsh, believe his personal accomplishments, especially his record five Super Bowl rings, make him worthy of induction into the Pro Football Hall of Fame. However, his history of unconventional and acerbic behavior during his playing days has not helped his candidacy. He was one of the fifteen finalists in 2010 and 2011; however, he was not selected. He was inducted into the Virginia Sports Hall of Fame in 2006. He was inducted into the College Football Hall of Fame in 2011 and the Texas Black Sports Hall of Fame in 2012.