BOSTON — The New England Patriots placed the franchise tag on Matt Cassel on Thursday.

The move means the quarterback remains a free agent, but the Patriots can match any offer made by another team or allow him to sign with that team in exchange for two first-round draft picks.

If and when he signs the one-year franchise tag designation, worth $14.65 million for 2009, he will be under contract to the Patriots, who could keep him or trade him.

Cassel's stock soared last season after he took over for Tom Brady, who suffered a season-ending knee injury in the opening game. Cassel helped the Patriots to an 11-5 record, but they missed the playoffs.

One factor in the Patriots' decision on whether to keep two highly paid quarterbacks is Brady's progress from knee surgery and the prospects for him being ready for the start of next season.

"Matt has been a pleasure to coach his entire career and last season in particular, when his years of hard work and commitment resulted in a most impressive performance," Patriots coach Bill Belichick said in a statement. "We look forward to working with Matt again in 2009."

David Dunn, Cassel's agent, did not return a call seeking comment.

Teams are allowed to place the franchise tag on one player per season. Without it, Cassel would have become an unrestricted free agent Feb. 27 and could have signed with any team without compensation to the Patriots. The period in which a team can designate a franchise player is Feb. 5-19.

The 26-year-old Cassel hadn't started a game in seven seasons — four at Southern California and three after New England chose him in the seventh round of the 2005 draft. He also struggled while taking most of the snaps in the 2008 exhibition season. But when Brady went down midway through the first quarter of the Patriots 17-10 win over Kansas City, Cassel responded.

He started the remaining 15 games and finished with 327 completions in 516 attempts (63.4 percent) for 3,693 yards, 21 touchdowns and 11 interceptions. The yardage was the fourth most in the AFC and the completion percentage was the third best in team history.

Cassel made $520,000 last season.

If the Patriots keep Brady and Cassel, they would have two quarterbacks taking up nearly 25 percent of the team's salary cap of $123 million for 2009. Brady's cap charge will be $14.62 million, although his actual salary for the year is $5 million with a $3 million bonus for making the roster.

Cassel is the fifth player in Patriots history to be designated a franchise player. The others were kicker Adam Vinatieri in 2002 and 2005, defensive back Tebucky Jones in 2003 and cornerback Asante Samuel in 2007. The Patriots waited until the last day to place the tag on all but Samuel, doing it six days earlier.

In 2002, the Patriots lifted the tag after they reached a multiyear agreement with Vinatieri. But he played under the tag in 2005 then left as a free agent for Indianapolis in 2006. In 2003, the Patriots traded Jones to New Orleans for three draft picks.

In 2007, Samuel held out of training camp until the Patriots agreed not to apply the tag to him again in 2008 if he played in 60 percent of the defensive snaps or they won 12 games in 2008. Both conditions were met and he left after that season for Philadelphia as a free agent.