As a junior, Alridge shared time at running back with the Cougars' senior Jackie Battle. Battle and Alridge combined for 1,762 rushing yards and 21 touchdowns during the 2006 regular season. After Battle graduated and signed a free-agent contract with the Kansas City Chiefs, Alridge assumed the bulk of the running back duties for Houston in 2007 and rushed for 1,597 yards on 259 carries (a 6.2 per-carry average) and scored 14 rushing touchdowns. He also caught 19 passes for 274 yards (a 14.4 average) and five touchdowns.