Seahawks coach Pete Carroll admires tenacity of Chiefs QB Matt Cassel

Matt Cassel embodies the path not traveled for Pete Carroll.

He is the quarterback Carroll didn't choose as the starter at USC back in 2003, the one who backed up two Heisman Trophy winners for the Trojans and never got the chance to start a single game at the school.

Cassel will start against his college coach on Sunday at Qwest Field, Cassel in his second year as the Chiefs starter and Carroll bubbling with enthusiasm for the guy who persevered even after he was passed over as USC's starter.

"To me it's an amazing story," Carroll said.

It is a story that spans eight years between starts for Cassel and includes one incredible workout on his college campus that got NFL scouts buzzing. Now Cassel has one of the most difficult jobs to attain in all of sports, a minted multimillionaire member of the elite fraternity of NFL starting quarterbacks.

It is the kind of story that you'd expect from Hollywood, and Cassel did graduate from the same high school as Val Kilmer and Kirk Cameron. Just one problem in putting Cassel's story on the silver screen: There'd be too much standing around. Cassel held a clipboard for years, first behind Carson Palmer, then Matt Leinart and finally Tom Brady.

A perpetual backup and a seventh-round draft pick, Cassel stepped in for New England after a season-ending knee injury to Brady and spun gold out of that opportunity. Now in his second year as Kansas City's starting quarterback, his Chiefs are 6-4 and he has thrown 18 touchdown passes compared to just four interceptions.

"I couldn't be more excited about him," Carroll said.

Because back in 2003, Carroll could have easily chosen Cassel over Leinart as the heir to Palmer.

"It was coming up on the spring game," Carroll said. "I was sitting there trying to figure out which way to go because both guys hadn't done very well in the spring. It wasn't obvious in any direction, so we go ahead with Leinart."

Impossible to argue with the results. Leinart led the Trojans to 35 victories in 36 games and two national championships.

"Obviously coach made the right decision," Cassel said.

Cassel wanted to play. Make no mistake about that. He played receiver and some special teams as a freshman and took a try at tight end later in his career. He even went out for baseball and showed enough promise that the Oakland Athletics drafted him in 2004.

But football remained at the forefront even while Cassel stood in the background.

"Like any competitor I would have loved to play and be able to play under coach there," Cassel said. "But it didn't work out. Sometimes you kind of just deal with what you're dealt."

Cassel played in 25 games at USC and threw 33 passes, but it was a workout on campus at the school's pro day that cracked open the backdoor in the NFL.

"All the workouts were done," Carroll said. "Matt hadn't thrown yet and he was going to stage a throwing session and show the scouts what he could do."

USC is the kind of school that commands the league's full attention. Mike Patterson would be chosen in the first round that year. Lofa Tatupu and Shaun Cody were second-round picks. Carroll estimated about half the scouts stayed to watch Cassel's workout.

"He hit everything," Carroll said. "Ripped the ball all around the field."

Cassel is 6 feet 4 with good mobility and a big arm so it wasn't like it was too tough to envision.

"There was definitely some appeal there for NFL teams," Tatupu said

Cassel had the NFL's attention after that workout, and in the seventh round the Patriots chose a quarterback who never started a game in college. Two years later, he started 15 games after Brady's knee injury, threw for 3,693 yards, and suddenly teams were pursuing him to start. The understudy's opportunity produced a season sufficiently impressive that the Chiefs traded a second-round pick for Cassel and linebacker Mike Vrabel.

And now he prepares to face his college coach, someone he said prepared him for the NFL even though Cassel never started for him.

"We had a lot of success while I was there underneath his guidance," Cassel said of Carroll. "I have nothing but the utmost of respect for him as a coach and as a person."

Danny O'Neil: 206-464-2364 or doneil@seattletimes.com