He's the one player they don't want to see in a game, especially the Super Bowl.
When the star quarterback was hobbling around on a sprained ankle last week, attention quickly turned to Cassel.
Who is he?
Is he any good?
Where did he come from?
"He's always been in situations where he's always been the man behind The Man," wide receiver Jabar Gaffney said. "He can play, though. He can definitely play."
"I hope I don't see him this weekend," Brady said with a smile, "unless he's kneeling down on the ball."
Brady is fine - he practiced Wednesday - which for now means Cassel will spend the Super Bowl the way he spends most football Sundays: on the sideline with a clipboard charting plays.
Cassel hasn't started a game at quarterback since he was a high school star in California. He went to Southern California and backed up Carson Palmer and Matt Leinart before being drafted in the seventh round in 2005 by New England, where he's firmly entrenched behind arguably the greatest quarterback in NFL history.
"I've got five different Heisman Trophy winners I played with," Cassel said. "I've got Carson, Leinart, Reggie (Bush), Vinny Testaverde, and even Doug Flutie my rookie year. I can't get away from them."
Brady wasn't a Heisman winner and was drafted only a round higher than Cassel, so he knows exactly what kind of patience it takes to keep from becoming frustrated.
"The thing about Matt, as soon as he gets the opportunity, everybody will see what he can do," Brady said. "It's hard to be a backup in our system. I don't like to let anybody to take any reps. I don't want anybody taking my job."
No worries there. But what if Cassel needed to play?
"We all feel here that if something were to happen to Tom that he could come in and do a good job for us," receiver Kelley Washington said.
Cassel has thrown 39 passes, including seven this season, and two touchdowns in his three-year NFL career. He also had a 15-yard scramble for a score in the Patriots' 52-7 rout of Washington early this season.
"Visualization is a big part of what I do," Cassel said. "If an instance like that where I had to come in were to come up, I try to visualize that - what the emotions and the energy and everything would be - and go out there and execute."
As a freshman at USC, Cassel appeared in seven games as a wide receiver and played on special teams. He got into 10 games as a backup quarterback in 2002, the year Palmer won his Heisman. Cassel competed with Leinart the following year for the starting job. Leinart got it, won the Heisman and led the Trojans to the national title.
"It was an intense battle between myself and Matt, and they obviously went the other direction," Cassel said. "It didn't happen, but at the same time, I'm here at the Super Bowl."
Where he's mostly answering questions about Brady.
"Yeah, I get, 'What's Tom like? Is he as good-looking as they say he is? How's his ankle? Is he playing Sunday?"' Cassel said with a laugh. "It's easy for me to say he's a great guy because there are nothing but good things to say about him."
With the spotlight brightly shining on the golden boy quarterback with the model girlfriend, no one would fault Cassel for wondering what life would be like if he were in Brady's shoes.
"No, I don't think about that," he said. "I've got a model wife. She's a great gal. I like my life just the way it is, and it's great."
"He's a guy who brings a lot of energy," receiver Chad Jackson said. "We're on the scout team and giving the defense a good look, and he's like, 'Let's do it like we're really getting offensive reps.' He really wants to be out there."
Cassel, who has two brothers playing minor league baseball, had a chance on the diamond, too. He played in the 1994 Little League World Series with the Northridge team that went to the finals. Ten years later, he pitched for USC, where his teammates included Yankees prospect Ian Kennedy.
"I only played one year," he said. "I was just trying to get out of spring football."
He went 0-1 with a 9.35 ERA in eight appearances, including one start, and was drafted by the Oakland Athletics in the 36th round of the 2004 draft. Cassel opted instead for the NFL.
"I don't know that I would enjoy all the minor league buses and going from one place to another and all the long bus rides," he said.
Cassel will take the trip to the Super Bowl over that any day, even if it's as the backup to The Man.
"Oh, yeah, he was born to be a quarterback," Washington said. "He was blessed to do that and he's made the right decision. His time will come."
Copyright 2008 by The Associated Press