The seven-year benchwarmer who finally slipped out of Tom Brady's shadow is unsure what the future holds. He could command a rich contract as a free agent. Or New England could put the franchise tag on its fill-in quarterback, assuring him of a huge pay raise.
Cassel does know this: forecasts often miss the mark.
"Nobody knows the future," he said Wednesday. "If anybody knew the future, I probably wouldn't be here right now because a lot of people predicted that I wouldn't be here after preseason. So the fact is nobody knows where I'm going to be next year.
"I could definitely be back here. So it's something that we'll have to wait and see."
The Patriots would be more likely to keep Cassel if they're uncertain that Brady will be fully recovered from a season-ending knee injury in time for next season. If they make Cassel their franchise player, he'd be paid the average of the top five quarterback salaries in the league after making $525,000 this season.
But that would be a lot of money to tie up in two players when only one can play at a time.
Would he like to be back?
"Of course I would," Cassel said. "I love the Patriots. I love this organization. Like I said before, I love the people."
Meanwhile, he's preparing for what could be his last game in a Patriots uniform. If they lose at Buffalo on Sunday, they'll be eliminated from playoff contention. And if they win and finish at 11-5, they'll make the playoffs only if Miami loses to the New York Jets or Baltimore loses to Jacksonville.
If they do advance, they can thank Cassel.
He never got a chance to prove himself at Southern California where he backed up Heisman Trophy winners Carson Palmer and Matt Leinart for two years each. It was more of the same after the Patriots drafted him in the seventh round in 2005 - three years of waiting behind Brady.
Cassel didn't start a single game in those seven seasons.
He performed poorly in exhibition games this year. So when Brady suffered a knee injury in the first quarter of the regular season opener, there was legitimate cause for concern - among fans.
He proved all of them wrong.
"I think it's great," Cassel said. "When you look back at the situation and you look at the naysayers and all the critics, it's great to overcome those obstacles and let people know that you never know what's going to happen in sports.
"For me, it's just a constant reminder (to) keep going out, working hard, be diligent about what you do, and good things will happen."
He became the fifth player in NFL history to throw for at least 400 yards in back-to-back games. He's thrown seven touchdown passes in his last two. He became the first player since the NFL-AFL merger in 1970 to throw for 400 yards and run for 60 in one game, a 34-31 overtime loss to the Jets on Nov. 13.
Since then, the Patriots are 4-1 and Cassel has risen to the 11th spot in the NFL in passer rating.
"It hasn't surprised me. I've always believed in myself and I've surrounded myself with positive-thinking people," he said. "That's why a lot of times I don't watch the sports shows or listen to the radio because of that simple fact, that there's too many critics out there and if you listen to everybody's opinion, I think it works against you."
The man whose opinion counts most believes in him. Coach Bill Belichick said Cassel needed a chance to play.
"I don't think anybody at the beginning of the year thought that, 'Oh, he just can't play,'" Belichick said. "There was some sentiment around about that outside this building, but I'm sure there wasn't any sense of that from the players or the coaches that worked with him."
Before the Patriots drafted Cassel, then-quarterbacks coach Josh McDaniels spoke to him several times. There was very little tape of him playing to evaluate, but he did get a strong recommendation from USC coach Pete Carroll, who coached the Patriots from 1997-99 before Belichick took over in 2000.
Carroll had pointed out "how competitive he was with Leinart and Carson Palmer," Belichick said. "All that being said, Matt's come a long way in four years and he's come a long way this year with the opportunity to play."
Cassel started slowly but has progressed each week.
"Did I ever foresee starting (15) games a season for the Patriots with Tom Brady here and everything else going on? I definitely would not say that," he said, "but I thought if I got all the reps throughout the course of the year I could steadily improve and win some ballgames."
Now he has a chance for a lucrative contract.
"That's a good deal, I think," he said. "Eight years and 180 and isn't that a guaranteed contract? I'm in the wrong sport here."
After three years on the sidelines, it finally turned out that he was with the right team. At least for this season.
"I don't know what the situation might be," Cassel said, "but the Patriots are home to me right now. That's all I've ever known in my professional career."