As a sophomore or "redshirt freshman" in 2010, Gardner saw action in 11 games on special teams and as a second-string defensive end.

He was named to the All-Pac-12 Conference 2nd Team,[5] and received Stanford's Deswarte-Eller Award honoring the most outstanding (redshirt) sophomore.

He chose to return to Stanford for a fifth year in 2013, rather than enter the NFL Draft, but it ended early because of a torn pectoral muscle he suffered against Oregon State University.

[9] On August 26, he was placed on the injured reserve list after having surgery to repair torn ligaments in his left shoulder.

The next year, the team brought in new talent at the defensive end position (Greg Hardy, Randy Gregory, Ryan Russell) and he was eventually waived on September 5, 2015.

[10] On November 4, 2015, Gardner was signed to the San Diego Chargers practice squad and switched to play outside linebacker in a 3-4 defense.