Tigers coach Johnny Jones said that Simmons did not start because "we had to address some academic stuff with him earlier in the week."
"This is just one of the attention getters for him," Jones said. "We're hopeful that this will help get him focused and concentrated on what he should be doing."
Simmons entered the game with 15:30 remaining in the first half, after the opening media timeout. He played 36 minutes and had 21 points and nine rebounds. He also had eight turnovers, matching his season high.
Jones revealed earlier this week that Simmons has been playing through a nagging finger injury on his shooting hand, but he told ESPN's Andy Katz on Friday night that Simmons' finger is fine.
Simmons, who is projected as a potential No. 1 overall pick in this year's NBA draft, entered Saturday's game leading LSU in points (19.3), rebounds (12.0), assists (5.1) and steals (1.9) per game.
The Volunteers also were without their leading scorer, Kevin Punter, who had a walking boot on his right foot Saturday after suffering an ankle injury two nights earlier in a loss at No. 14 Kentucky. Punter is averaging 22.2 points per game and entered the day as the 10th-leading scorer among all Division I players.
Tennessee coach Rick Barnes said after Saturday's game that Punter's status is day-to-day.
Information from The Associated Press was used in this report.