Tom E. Curran • E-mail

Six months ago, he barely made the Patriots roster coming out of training camp. Thursday, he was declared the team’s franchise player.

The curious case of quarterback Matt Cassel continues.

It’s been a wild ride from there to here, and the most intriguing part of it is why it happened.

Cassel, who just completed his fourth season at a relatively modest $520,000 salary, would have been a free agent if New England didn't use its franchise tag on him, which will guarantee him a 2009 salary of $14.65 million.

On the open market, the 26-year-old quarterback would have commanded a deal comparable to the ones given to a top-five quarterback coming out of college — something in the range of five years and $50 million with $25 million guaranteed.

It’s an amazing turn of events for Cassel, who struggled so mightily in training camp that New England contacted and planned to work out unemployed quarterbacks Tim Rattay and Chris Simms during the first week of the season. But once Tom Brady went down with a blown left knee, the team was Cassel’s, for better or worse.

And it was for the better.

Cassel led the Pats to an 11-win season, throwing for almost 3,400 yards with 21 touchdowns and 11 interceptions. Because of that, the Patriots didn't want to part with Cassel too quickly.

Special feature Who may get tagged? Curran: Franchise tags likely to hit these players

There are two reasons the Pats wanted to control Cassel’s future at such a steep price.

First, he serves as insurance for Brady, who continues to rehab from a torn ACL and MCL and an infection that halted the early part of his rehab.

Second, if the team is convinced Brady will be full-go in September of 2009, Cassel becomes trade bait.

Cassel was declared a “non-exclusive” franchise player, which means other teams can negotiate with him, but they’ll have to compensate the Patriots with two first-round picks. Cassel, who backed up a pair of Heisman Trophy winners at USC and before this season hadn’t started a game since high school, was a seventh-round pick by New England in 2005. That’s a significant appreciation on the initial investment.

Or, more likely, a team can work out a trade with New England and sign him to a long-term deal.

That’s what happened last season with current Vikings defensive end Jared Allen. The Kansas City Chiefs made Allen their franchise player, but Minnesota sent the Chiefs draft picks (a first and two thirds, plus an exchange of sixth rounders) and then signed him to a six-year, $72.36 million deal with $15.5 million guaranteed. 

Slideshow   The Week in Sports Pictures The Giants on top of the football world, getting ready for the London Olympics and more. more photos

New England faced a conundrum. Did they feel confident enough that Brady’s knee, which developed a since-cleared infection soon after surgery and may never be as strong as it was before, was sturdy enough to let Cassel go? At this point, no.

Did they think that Cassel’s stock will never be higher than it is right now, which could result in a draft pick bounty? That can still happen.

At worst, they'll try to get Cassel to negotiate a short-term deal to keep him around in 2009 at a reduced rate since carrying him at $14.65 million and Brady at his 2009 salary of $14.6 million would eat up 23 percent of the team’s $123 million cap space.