I would like to believe that Matt Cassel can do in 2008 what Tom Brady did in 2001.

Really, I would. Because who, back then, would have believed that Brady could come off the bench after playing in just one game as a rookie — in which he completed one of three passes for six yards against the Lions on Thanksgiving Day in Detroit — and lead the Patriots to the NFL championship?

What Brady did that unforgettable season was simply unbelievable.

It was a story that, if a scriptwriter had submitted it to a Hollywood movie studio, would have been rejected as too far-fetched. Either that, or as too much like The Natural — an implausible, impossible storyline featuring Brady as a Roy Hobbs in cleats instead of spikes, and with a golden arm rather than a special bat.

After all, Brady had been only a sixth-round draft choice out of the University of Michigan. The guy he replaced in the second game of that 2001 season, Drew Bledsoe, had been the first player taken in the entire draft in 1993.

Bledsoe had led the Pats to the playoffs in only his second season, 1994, and to the AFC championship in 1996, when, with Bill Parcells as coach, they lost to Brett Favre and the Packers in Super Bowl XXXI in New Orleans.

But the fortunes of the Patriots went downhill after that, when Parcells left New England for the New York Jets and was replaced by Pete Carroll. Three years and just one postseason win later, Carroll was replaced by Bill Belichick, who lost his first four games in 2000 and finished 5-11.

The Patriots lost their opener in 2001, and wound up losing to the Jets in the home opener, 10-3, after Bledsoe was knocked out of action by a devastating blow to the chest delivered by N.Y. linebacker Mo Lewis.

At that point, the Pats had lost 13 of Belichick’s first 18 games, all with Bledsoe at quarterback. Was there any reason to believe the team would be better with Brady under center?

Although New England upset Indianapolis at Foxboro in Brady’s first start, routing Peyton Manning and the high-scoring Colts, 44-13, Tom wasn’t consistently terrific. He struggled in a 30-10 trouncing in Miami the following week, and threw four interceptions at Denver three weeks after that.

The Patriots were 5-5 following a loss to the Rams in a Sunday night game in Foxboro but, even at that, Brady had exceeded most people’s expectations. Most people also were expecting Bledsoe, who by then was ready to play, to return to the lineup the following week against New Orleans.

But Belichick liked what he had seen of Brady and decided to stick with him, despite the old NFL standard that insisted a starter shouldn’t lose his job because of injury — especially a starting quarterback.

The coach was right, as the Patriots didn’t lose again that season. They won their final six regular-season games, edging Oakland in the snow in the conference semifinals in Foxboro when Brady’s apparent fumble was ruled a forward pass, stunned the Steelers in Pittsburgh in the AFC Championship Game when Bledsoe came off the bench after Brady was banged up and threw a TD pass, and then, with Brady again at the helm, shocking the Rams — billed as “The Greatest Show on Turf” — in Super Bowl XXXI, 20-17.

Brady was named MVP of that game — and of Super Bowl XXXIX, when the Pats won their second straight championship, and third in four years. He took them to the AFC Championship Game in 2006, and set an NFL record by throwing 50 touchdowns in last year’s perfect, 16-0 regular season, which, after two more playoff wins, ended in disappointment with a last-minute loss to the Giants.

I’d like to believe Cassel can do something like that.

But I can’t.

There’s only one Tom Brady, while Cassel has been a No. 2 quarterback since he graduated from high school.

This Sunday’s game against Favre and the Jets at the Meadowlands will be Cassel’s first start since he was at Chatsworth (Calif.) High in 1999 and lost in the playoffs. At Southern Cal, he played behind two Heisman Trophy winners — Carson Palmer, who now is the QB for the Bengals, and Matt Leinart, who is a backup in Arizona behind veteran Kurt Warner.

Despite his lack of experience, Cassel was drafted by New England in the seventh round in 2005, and the Pats have hung on to him, even though many members of the media covering the team thought he might be cut at the end of training camp in favor of Matt Gutierrez and third-round draft choice Kevin O’Connell.

Once again, though, Belichick’s decision-making proved correct, as Cassel came off the bench against Kansas City midway through the first quarter and, starting with a 51-yard bomb to Randy Moss on third-and-11 from his own one-yard line, performed quite capably in a nail-biting New England victory that wasn’t locked up until recently acquired cornerback Deltha O’Neal batted away in the end zone a fourth-down pass from the five-yard line in the closing seconds.

But there are 15 games to be played, and most of the opponents will be tougher than the Chiefs. After racking up a record number of points last year with Brady throwing to the likes of Moss and Wes Welker, the Pats’ point production is likely to plummet with Cassel at the controls, which could prove problematic since the New England secondary is suspect.

There’s no reason to believe that the Patriots can’t still win the AFC East, although the Jets, and even the Bills, undoubtedly believe their chances of wresting the division title away from New England have improved considerably.

I’d like to believe the Patriots still can win the Super Bowl — that Cassel can do in 2008 what Brady did in 2001.

But I can’t.

jdonalds@projo.com