As a senior linebacker, he received second-team All-state, SuperPrep All-American, All-area and All-county honors.
As a freshman, he appeared in 8 games, starting 6 at strongside linebacker, while recording 31 tackles (one for loss) and 1.5 sacks.
As a sophomore, he was named the regular starter at strongside linebacker, tallying 74 tackles (second on the team), one sack, 5 passes defensed, 5 forced fumbles (school record) and one blocked punt.
Singleton was selected by the Tampa Bay Buccaneers in the fourth round (128th overall) of the 1997 NFL draft.
He suffered a knee injury in the 13th game against the Dallas Cowboys, which forced him to miss the final 3 contests of the regular season.
He also contributed to the team having the league's top ranking defense and winning Super Bowl XXXVII.
On March 13, 2003, he signed with the Dallas Cowboys as a free agent to take over the starting strongside linebacker position, that was previously handled by the departed Kevin Hardy.
In 2005, the team switched to a 3-4 defense, but he was still able the remain the starter at the left outside linebacker position, until suffering a broken clavicle against the Arizona Cardinals during the week 8 and being placed on the injured reserve list on November 1.