THE START OF A LIFETIME

For the last eight years, Matt Cassel has been a quarterback for some of football’s most successful college and professional teams, at USC and for the New England Patriots.

He knows what it is to win a college national championship, knows the feeling of making it to the Super Bowl.

Yet, because he hasn’t started a game since his senior season at Chatsworth High in 1999, many football fans might not even be sure how to pronounce the 26-year-old’s last name.

For the record, Cassel is pronounced like “castle,” and at the moment he’s the accidental prince of the Patriots, thrust into the starting lineup after two-time Super Bowl MVP Tom Brady suffered a season-ending knee injury in the opener.

Cassel, a onetime Little League baseball star, is now on deck for the biggest football game of his life.

Taking the wheel of the NFL’s Maserati against the hated rival New York Jets -- with Brett Favre making his regular-season debut at the Meadowlands, no less -- might sound overwhelming for someone with precious little experience. But that’s not how people who know Cassel well are thinking.

“Even though Matt didn’t have the strongest of preseasons, and he’ll tell you that, there’s a reason that he made the final cut,” said Steve Clarkson, a respected quarterback tutor who has worked as Cassel’s private coach since the summer before he started at USC.

“The Patriots see him every day and they’ve watched him for the last three years, and they know what they have in Matt Cassel, the things he had in him when they drafted him. It’s no secret to them.”

Cassel’s most recent start at quarterback came in a City Invitational quarterfinal game at Palisades High in November 1999, when he doubled as a defensive back. Clarkson was on the opposing sideline, working as Palisades’ offensive coordinator.

Chatsworth hardly threw in that game -- Cassel completed three of 11 passes for 46 yards -- and its star was running back Samuel Wesley, who ran for 290 yards and four touchdowns.

If there was a quarterback who appeared headed for bigger things, it was Palisades’ David Koral, who threw for 424 yards and four touchdowns, paving the way for a 49-42 victory. Koral wound up as a reserve at UCLA.

At the time, Clarkson figured Cassel would wind up a head-knocking safety.

“I actually thought he was going to be the next John Lynch,” Clarkson said, referring to the Pro Bowl safety. “He single-handedly put out two of our top receivers with just vicious hits. You could close your eyes and listen for the collision, and you knew just by the sound of the impact who hit him.”

Even though Palisades won the game, Clarkson said, “We basically lost the following week just because of the effects of Matt Cassel from the week before.”

There weren’t many high school seniors who had the type of big-stage sports experience Cassel had at that point. At 12, Cassel was on the Northridge baseball team that reached the finals of the 1994 Little League World Series in Williamsport, Pa. And in high school championship games his junior year at Chatsworth, he played quarterback at the Coliseum and designated hitter at Dodger Stadium.

Truth be known, baseball is the sport of choice in the Cassel family. Matt, who’s married to former USC volleyball player Lauren Killian, was selected by the Oakland Athletics in the 36th round of the 2004 Major League Baseball draft. He has a sister, Amanda, and two brothers, Jack and Justin. Jack is a pitcher for the Houston Astros; Justin pitches for the Birmingham Barons, a double-A affiliate of the Chicago White Sox.

Just as he could have pursued a career in baseball, Matt also could have left USC when it became increasingly obvious that he was destined to be a backup. After Carson Palmer left and was selected No. 1 overall by Cincinnati, it was clear that offensive coordinator Norm Chow was going with Matt Leinart as the successor.

Willing to do just about anything to get onto the field, the 6-foot-4, 230-pound Cassel even tried moving to tight end for the Trojans, but that experiment was short-lived.

“It takes a lot of perseverance, fortitude and confidence to stick in there and say, ‘Hey, I know I’m good, and I’ll make it through this,’ ” said Ken O’Brien, the former NFL quarterback and coordinator who later worked as a USC assistant coach and helped recruit Cassel. “He just stuck it out.”

Eventually, it paid off. Cassel got such high marks from his coaches and was so impressive to scouts during testing at USC’s annual “pro day,” the Patriots selected him in the seventh round of the 2005 draft. And Clarkson said there were two or three teams ready to take him had the Patriots not done so.

USC Coach Pete Carroll said Cassel’s three seasons behind Brady should serve him well this season.

“This is not a guy that’s going to get thrown to the wolves, that hasn’t really had the opportunity to learn the system,” Carroll said. “He’s really athletic. He’s tough. He has a great arm. He knows what’s going on. He’s got a beautiful team around him. It will be interesting to see how the chemistry works now. It’s a great challenge.”

Cassel did his part to bail out the Patriots after Brady was injured during the first quarter against Kansas City. Minutes later, with his team facing a third and 11 from its own 1, Cassel faked a handoff to Sammy Morris and floated a pass down the sideline to Randy Moss for a 51-yard gain. The All-Pro receiver had broken off his route to the right when he spotted a vulnerability in the coverage.

The play was Brady-esque, set up New England’s first touchdown, and allowed Cassel to exhale.

“After that pass,” Cassel later told reporters, “it definitely calmed the nerves down a bit, and I said, ‘I can do this.’ ”

New England went on to win, 17-10, and though the Chiefs figure to be among the NFL’s bottom dwellers, Cassel put up respectable numbers, completing 13 of 18 passes for 152 yards and a touchdown with no turnovers. This after an exhibition season in which the Patriots were scoreless in the 17 series he led the offense.

About 3,000 miles away, listening to the game on the radio, was Tom Meusborn, who coaches baseball at Chatsworth. His reaction was probably similar to that of other Cassel friends and family members, saddened by the injury to Brady but elated that a very special backup was finally getting his chance.

“I was driving home from school when I heard Brady was hurt, so I turned to the game,” Meusborn said. “When I heard Matt throw that touchdown pass I was just so excited for him. I was mowing the lawn, and I had to stop what I was doing. I yelled out a little bit. The neighbors were like, ‘Tom? You OK?’ ”

Meusborn was better than OK. The long wait over, Cassel’s pro career was officially underway.

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Times staff writer Gary Klein contributed to this report.

sam.farmer@latimes.com

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New England

vs. N.Y. Jets

Sunday at the Meadowlands

1:15 p.m., CBS or DTV 714