Crompton was briefly a member of the NFL's New England Patriots, Tampa Bay Buccaneers, and Washington Redskins.

[4] In 2005, Crompton enrolled at the University of Tennessee to play college football under head coach Phillip Fulmer.

[5][6] In 2006, Crompton saw little action until an injury to starting quarterback Erik Ainge led to his first significant playing time against #13 LSU.

Replacing Ainge in the second quarter, he threw for 183 yards, two touchdowns, and an interception in the Volunteers' 28–24 loss at Neyland Stadium.

He threw his lone touchdown of the season, a 49-yard pass to wide receiver Kenny O'Neal, in a 59–7 home victory over Louisiana-Lafayette.

[17] When Lane Kiffin was hired as head coach of the Volunteers, he named Crompton the starting quarterback prior to the 2009 season.

In Kiffin's first game as the Volunteers' head coach, Crompton had a great outing with 233 passing yards, five touchdowns, and two interceptions in the 63–7 home victory over the Western Kentucky Hilltoppers.

[20][21] Crompton led Tennessee to an upset 45–19 home rout of the Georgia Bulldogs[22] and was named the AT&T National Player of the Week.

[40] On August 22, 2014, he played his first game for the Alouettes in relief of Alex Brink, completing 18 for 29 passes for 266 yards in a 24–16 loss to the Winnipeg Blue Bombers.

During the 2014 CFL season, Crompton completed 179 passes on 308 attempts (58.1% accuracy), for 2,482 yards, with 11 touchdowns and eight interceptions (passer rating of 85.2).

Crompton had a rough start to the 2015 CFL season: On opening night, he completed just 5-of-17 pass attempts for 51 yards with one touchdown and one interception.

On January 18, 2022, it was announced that Crompton had joined the Bishop's Gaiters as the team's offensive coordinator and quarterbacks coach.

[47] On March 27, 2023, it was announced that Crompton had been named head football coach of Tuscola High School in Waynesville, NC.