He played running back for the Texas Tech Red Raiders and in the NFL for six seasons, primarily with the Denver Broncos where he won Super Bowl XXXII and XXXIII.

The 6 ft 3 in (1.91 m) Lynn played at Celina High School, and later for the Texas Tech Red Raiders (1988–1991), where he was an All-Southwest Conference running back in 1990.

Lynn was a journeyman reserve running back and special teams player during his NFL career, playing for the Denver Broncos (1993, 1997–1999) and San Francisco 49ers (1995–1996).

[2] After leaving Jacksonville, Lynn quickly joined the Dallas Cowboys staff as the running backs coach.

[6] On September 16, 2016, Lynn was promoted to assistant head coach and offensive coordinator of the Bills when Greg Roman was fired.

[15] In January 2016, Lynn was a head coaching candidate for the San Francisco 49ers,[16] but removed his name from consideration before a decision was made.

[22] In his second season as the Chargers head coach, Lynn led Los Angeles to a 12–4 record, earning its first playoff berth since 2013.

[29] Lynn gained the additional title of running backs coach when Bobby Turner stepped away to address health issues.

[31] Following the 49ers' loss in the 2023 NFC Championship Game, the Washington Commanders were granted permission to interview Lynn for their vacancy at offensive coordinator in February 2023.

[35] His son, D'Anton, played college football for the Penn State Nittany Lions, and was signed as an undrafted rookie by the New York Jets following the 2012 NFL draft.

Lynn was supportive of his son's decision to follow in his footsteps, and taught him about the hard work that goes into being a professional football player both on and off the field.

[37] Lynn and Todd Haley, both offensive assistants for Bill Parcells, were out for pizza after training camp in Ventura, California.