Kalen Bruce Thornton (born May 12, 1982, in Dallas, Texas) is a former American football linebacker in the National Football League for the Dallas Cowboys. He played college football at the University of Texas. Early years Thornton attended St. Mark's School of Texas. He played 2 years at fullback. As a senior, he was converted into a linebacker and also played. He recorded 86 tackles, 16 sacks, 4 fumble recoveries, 2 forced fumbles and 24 carries for 232 yards. During his three seasons, he helped the team achieve a 26–3 record and win a league title. He also practiced basketball and track College career Thornton accepted a football scholarship from the University of Texas at Austin. As a true freshman, he started 9 games at defensive end, collecting 32 tackles (17 solo), 3.5 sacks (tied for fifth among freshman in school history), 8 tackles for loss (tied for fifth among freshman in school history) and 20 quarterback pressures. As a sophomore, he started 11 games, making 44 tackles (11 for loss), 4 sacks, 20 quarterback pressures (led the team) and one forced fumble. He suffered a knee injury in the fifth game against the University of Oklahoma. As a junior, he regained his starter position after coming back from offseason knee surgery, tallying 28 tackles, 2.5 sacks, 5 tackles for loss, 14 quarterback pressures and a blocked extra point in 10 games. He also suffered a sprained ankle midway through the season. As a senior, he missed spring practice recovering from reconstructive surgery on his right knee. He posted 51 tackles (9 for loss), 4 sacks, 21 quarterback pressures and 6 passes defensed. He had 10 tackles in the 2003 Holiday Bowl. He finished his college career as a four-year starter, starting 35 out of 46 games (including bowl games), posting 155 tackles (33 for loss), 14 sacks and 75 quarterback pressures. Professional career Thornton was signed as an undrafted free agent by the Dallas Cowboys after the 2004 NFL Draft, dropping because of his knee injury history. As a rookie, he was converted into an outside linebacker, posting 8 defensive tackles, one quarterback pressure and 13 special teams tackles (sixth on the team). In 2005, he was expected to compete for the starting job against rookie DeMarcus Ware, but he suffered a left knee injury in training camp that required career-ending microfracture surgery and was placed on the injured