COLUMBUS, Ohio -- Troy Smith will start for the No. 9 Buckeyes on Saturday against San Diego State, while Justin Zwick -- the starter the first two games this season -- has been relegated to the sideline.

Coach Jim Tressel said he couldn't even say for sure if Zwick will play against the Aztecs.

It was difficult to tell who was in charge of the offense and what the game plan was during Saturday's 25-22 loss to Texas, as Tressel shuffled in quarterbacks like relief pitchers in a high-scoring game.

Tressel has been criticized on call-in shows and in chat rooms since the defeat.

"You have to make decisions," Tressel said Tuesday. "I've never pretended that every decision I've made was right. And I've been reminded of that."

Tressel waffled throughout the nationally televised game with No. 2 Texas, playing Zwick the first two series, then Smith for five, then Zwick for two, Smith for one, Zwick for two, and Smith for one. As a result, the offense never really got into a rhythm.

"There were some times when I didn't execute," Tressel said, discussing how well he coached during the game. "You have to start with yourself in the formula. I certainly didn't grade a winning performance."

Smith was 5-for-11 for 78 yards and a touchdown and added 13 rushes for 27 yards. He led Ohio State to points on five consecutive possessions and a 19-13 lead, then was suddenly replaced by Zwick.

The Buckeyes scored three points on drives with Zwick at quarterback. He ended up 9-of-15 for 66 yards and gained 11 yards on five carries. He fumbled the ball the last time he touched it, all but snuffing out Ohio State's final chance.

Tressel said after the game that he substituted quarterbacks based on his feelings at the moment. On Tuesday, he did not give concrete reasons for giving Smith the job.

Texas coach Mack Brown, speaking at his weekly news conference in Austin, said he was impressed with both Ohio State quarterbacks and understood the dilemma facing Tressel.

"The toughest thing that can happen is you play them both and lose," Brown said. "It just opens you up for criticism. It's a very difficult thing."

Smith said no one had told him he was starting against San Diego State, but if that was the case he would relish the opportunity. He said he needed the extra repetitions in practice this week to get back into playing shape.

"It means a lot for anybody," he said of the starting assignment. "The more reps you're going to get, the better you're going to be. Sharing is OK, but you've got to make the best of your reps when you get them. When you know with certainty that you're going to go, you're able to focus a little bit more."