Williams will forego his senior season and enter the 2011 NFL Draft.
"I want to thank everyone at The University of Texas, especially Coach (Mack) Brown and Coach (Duane) Akina for getting me ready for this opportunity," Williams said. "It was a really hard decision. I'm going miss to all of my teammates and coaches, and I'll always be a Longhorn, but I felt it was the best decision for me and my family. It's time to start working on my dream that I've been preparing for all my life."
Williams was selected to the Nagurski Trophy and Thorpe Award watch lists early on in 2010, but despite making several big plays, Williams was a member of a secondary that failed to live up to expectations. He earned second-team All-Big 12 honors while starting nine of 11 games. He missed a game after sustaining a concussion.
Williams led the team with 13 passes broken up, while making 46 tackles, one sack, five tackles for loss, three forced fumbles and one blocked punt.
Williams's three forced fumbles were tied for third in the Big 12.
An NFL scout told LonghornDigest.com that Williams currently projects as a third-round pick, though the scout acknowledged that Williams, who possesses ideal measurables, could see his stock jump with an excellent workout.
Williams first earned a starting position in 2009, and started 23 of the last 26 games of his career. Williams finished his Longhorn career with 106 stops (64 solo), three sacks, 12 tackles for loss, three pressures, four interceptions, 24 passes broken up, six forced fumbles, one fumble recovery and five blocked punts in 37 games. Those blocked punts put him No. 2 on the UT career list.
Williams was considered among the best nickel backs in the Big 12, a big cornerback who excelled as a tackler, playmaker and cover man.
"Aaron was a tremendous football player who helped us win a lot of games here," head coach Mack Brown said. "We have had great success with our defensive backs in the NFL and expect the same for Aaron. We will really miss having him around next year and know it was a tough decision, but look forward to following his career in the NFL."
Williams's departure leaves the Longhorns with an inexperienced cornerback group for the 2011 season, with true sophomores Carrington Byndom and A.J. White ranking as the top remaining players on the depth chart. In addition to Williams, the Longhorns will be without Curtis Brown and Chykie Brown, who graduated following the 2010 season.
Eight former Texas defensive backs under Brown and Akina are currently playing in the NFL. The group includes Tarell Brown (San Francisco 49ers), Cedric Griffin (Minnesota Vikings), Michael Griffin (Tennessee Titans), Michael Huff (Oakland Raiders), Quentin Jammer (San Diego Chargers), Aaron Ross (New York Giants), Earl Thomas (Seattle Seahawks) and Nathan Vasher (Detroit Lions). All eight have served as NFL starters.