He played college football for the Notre Dame Fighting Irish and was selected by the Carolina Panthers in the second round of the 2010 NFL draft.

In 2006, he threw 49 touchdown passes for the season to lead the Lions to their first ever Division III state title over Cardinal Newman High School (Santa Rosa, CA).

Beginning in eighth grade, his parents paid his tutelage under professional quarterbacks coach Steve Clarkson.

[7] Recruiting analysts considered him a "once in a decade" quarterback talent and ranked him as the #1 overall prospect of the 2007 high school class.

[9] Many of these critics pointed to the 2007 U.S. Army All-American Bowl in which Clausen was outplayed by fellow 2007 quarterback recruit, Ryan Mallett.

[10] Further, Clausen's age is a subject of criticism: he started kindergarten at six and repeated sixth grade,[7] thus he was 19 years old at the time of his early graduation.

[13] Clausen announced his verbal commitment at the College Football Hall of Fame in South Bend, Indiana, after arriving in a stretch Hummer limousine.

[17] In Notre Dame's only preseason practice open to the media, Clausen threw only a number of short passes, casting some doubt on the strength of his arm after off-season elbow surgery.

Citing non-specific injuries to Clausen (who had been sacked 23 times), head coach Charlie Weis named Sharpley as the starting quarterback for Notre Dame's game against USC on October 20, 2007.

[21][22] After sitting out Notre Dame's losses to USC and Navy, Clausen was again named the starter for their game against Air Force.

[24] During his sophomore season, he completed 60.9% of his passes for 3172 yards, 25 touchdowns and 17 interceptions and a 132.5 efficiency rating which placed him as the 44th ranked quarterback in NCAA Division I FBS.

[28] On Monday, December 7, 2009, Clausen declared that he would forgo his senior season at Notre Dame and enter the NFL draft following news of the firing of head coach Charlie Weis.

[39] Clausen made his NFL debut in a loss against the New York Giants in the 2010 season opener, after starting quarterback Matt Moore was sidelined with a concussion.

[41] The following week, Clausen started his first NFL game against the Bengals, completing 16 of 33 passes for 188 yards and an interception and three fumbled snaps, losing two.

[41] During the game TV cameras caught wide receiver Steve Smith walking over to Clausen, who was talking with an assistant coach, and screaming at the rookie.

He also started in a December 20 game against the Kansas City Chiefs, in which he completed 26 of 45 passes for 281 yards, with two touchdowns and two interceptions, in the 34–14 loss.

[55] Clausen was then benched for Ryan Mallett, who led the Ravens to a 20–17 upset win over the rival Pittsburgh Steelers the following week.

According to published reports, Clausen entered a pre-trial diversion program that erased the citation since he stayed out of trouble for the following 12 months.