Win more games, Hesiman Trophy winner Matt Leinart said.
The Trojans are 7-3.
"Losses hurt, it doesn't matter what team you're on," said Leinart, who lost only two games in three seasons as USC's starting quarterback. "You've got to win games, especially as a quarterback."
Kessler has passed for 29 touchdowns, with three interceptions.
He has completed 70% of his passes.
Leinart, the 2004 Heisman winner, is a college football analyst for Fox Sports. Kessler was "very underrated," he said.
"He's a couple plays away from being a top-10 team and a Heisman candidate in my eyes," said Leinart, adding that Kessler should be a front-runner for the prestigious award next season.
"His numbers are terrific, I think he's a great leader and he's still only a junior," Leinart said. "He still has another year left, which is pretty scary."