LeFors was selected by the Carolina Panthers in the fourth round (121st overall pick) of the 2005 NFL Draft out of the University of Louisville.
After serving one season in a backup role, he was released by the Panthers in September 2006.
LeFors conducted workouts for the Tampa Bay Buccaneers, Minnesota Vikings, Seattle Seahawks, Buffalo Bills, Detroit Lions, Oakland Raiders, and Denver Broncos but was not offered a contract.
In December 2006, LeFors was signed by the Edmonton Eskimos of the CFL as an import player.
He was the backup quarterback for the team's 2007 season, but had the opportunity to start 5 games at the end of the season because of Ricky Ray's shoulder injury.
By the end of the 2007 CFL regular season, LeFors was placed 8th in the league in passing yardage with 1193 yards, as well as 6 touchdowns and 8 interceptions, while completing 60.8% of his passes.
He was 7th in quarterback rushing yardage with 204 yards and 2 touchdowns.
His best performance of the season came in week 18 against Saskatchewan.
In a losing effort, he managed to complete 34/48 passes for 412 yards 3 touchdowns and 1 interceptions, while scrambling 6 times for 31 yards.
According to head coach Danny Maciocia, LeFors shares the job as 2nd string quarterback on the Eskimo depth chart for the 2008 campaign with Jason Maas.

On January 21, 2009, LeFors was traded to the Winnipeg Blue Bombers for a second-round pick in the 2009 CFL draft and a conditional selection in 2010.
Then on June 18, 2009 LeFors was named Winnipeg's starting quarterback for the start of the 2009 season.
In the offseason preceding the 2010 CFL season, LeFors retired from the CFL.
LeFors was selected by the Carolina Panthers in the fourth round (121st overall pick) of the 2005 NFL Draft out of the University of Louisville. After serving one season in a backup role, he was released by the Panthers in September 2006. LeFors conducted workouts for the Tampa Bay Buccaneers, Minnesota Vikings, Seattle Seahawks, Buffalo Bills, Detroit Lions, Oakland Raiders, and Denver Broncos but was not offered a contract. In December 2006, LeFors was signed by the Edmonton Eskimos of the CFL as an import player. He was the backup quarterback for the team's 2007 season, but had the opportunity to start 5 games at the end of the season because of Ricky Ray's shoulder injury. By the end of the 2007 CFL regular season, LeFors was placed 8th in the league in passing yardage with 1193 yards, as well as 6 touchdowns and 8 interceptions, while completing 60.8% of his passes. He was 7th in quarterback rushing yardage with 204 yards and 2 touchdowns. His best performance of the season came in week 18 against Saskatchewan. In a losing effort, he managed to complete 34/48 passes for 412 yards 3 touchdowns and 1 interceptions, while scrambling 6 times for 31 yards. According to head coach Danny Maciocia, LeFors shares the job as 2nd string quarterback on the Eskimo depth chart for the 2008 campaign with Jason Maas.
On January 21, 2009, LeFors was traded to the Winnipeg Blue Bombers for a second-round pick in the 2009 CFL draft and a conditional selection in 2010. Then on June 18, 2009 LeFors was named Winnipeg's starting quarterback for the start of the 2009 season. In the offseason preceding the 2010 CFL season, LeFors retired from the CFL.
Stefan LeFors