"They were really even," Robinson said this week. "Both were very capable."

Robinson and Riley expected that one of the quarterbacks would separate from the other once the season began. "But they both played well," Robinson said, "so they both played."

Otton started 10 of 12 games and passed for 14 touchdowns with four interceptions. Wachholtz started twice and passed for 11 touchdowns with three interceptions.

"At first, you think everyone is eyeing you on the sideline and keeping track of what each guy is doing," Otton said. "But then you realize no one is pulling for one guy or the other. They just want to win."

There were games in which one quarterback played more than the other because of injury or performance. Otton played the entire game in the 41-32 Rose Bowl victory over Northwestern.

He said alternating takes a mental toll on quarterbacks.

"You want to be a team guy and root for the other guy to do well," he said. "If he goes in there and throws two touchdowns, you're happy for the team but you're also saying, 'Dang, I might not get in the game again.'

"It plays with your head."

Riley is now head coach at Oregon State, and he has said he will also play two quarterbacks — Sean Mannion and Cody Vaz — in the Beavers' opener against Eastern Washington.

However, he also recently told ESPN that he had "regrets about that game," referring to his and Robinson's decision to stick with Otton and not play Wachholtz at all in USC's Rose Bowl victory over Northwestern.

Robinson now works for USC's Trojan Athletic Fund and as a college and pro football radio analyst. After observing Wittek and Kessler during several training-camp practices this month, he said playing both might be the best thing for the Trojans. At least for now.

"People say we need one guy to be a leader. Hell, you need a guy to play well at quarterback," Robinson said. "He could speak a different language or whatever.

"Just go out and play well."

gary.klein@latimes.com

Twitter: @latimesklein