Mitch Mustain has a backup plan

When quarterback Mitch Mustain visited USC while pondering a transfer from Arkansas in February 2007, he cited former backup Matt Cassel as a reason for considering the Trojans. Regardless of whether he started at USC, Mustain reasoned, the program would prepare him well for the NFL.

Cassel's recent play, including a 400-yard passing performance in the Patriots' recent 34-31 overtime loss against the New York Jets, strengthened Mustain's belief that it can work out for a backup.

"It's nice to see a guy who's gone in and put the work in and delivered when he finally got his break," said Mustain, who has been second on the depth chart behind Mark Sanchez since the Oct. 4 game against Oregon.

Mustain has played in six games, completing 10 of 14 passes for 150 yards and two touchdowns.

Cassel never started a game for USC while playing behind Heisman Trophy winners Carson Palmer and Matt Leinart. The Patriots selected him in the seventh round of the 2005 draft and he spent three seasons backing-up Tom Brady.

But when Brady suffered a season-ending knee injury in this season's opener, Cassel was thrust into the starting role. He has passed for 2,200 yards and 10 touchdowns with seven interceptions.

Cassel will be an unrestricted free agent after the season and stands to hit the jackpot on the open market or with the Patriots.

"He's struggled and been dogged here and there but he's had his chance and done pretty well," Mustain said.

Klein is a Times staff writer.

gary.klein@latimes.com