The Green Bay Packers quarterback carousel continued to spin Monday, and Matt Flynn is the latest to jump aboard.

Flynn, the team's seventh-round draft choice in 2008 and backup to Aaron Rodgers for four seasons, became the fourth quarterback the Packers have had on the 53-man roster this season.

According to an NFL source, Flynn signed with the Packers early Monday evening after working out for them in the morning. The signing occurred after business hours, so the Packers did not announce it and won't be required to make a corresponding roster move until the end of the business day Tuesday.

As fast as the ride has spun since Rodgers went down with a broken left collarbone against Chicago last week, Scott Tolzien, the young backup who played surprisingly well Sunday against Philadelphia, is seated firmly in front.

Coach Mike McCarthy announced that Tolzien would be his starter against the New York Giants on Sunday and did not back away from that Monday. He expressed his admiration for what Tolzien did despite it being his first NFL game and getting barely any practice time.

"I thought he played an outstanding football game based on the amount of preparation," McCarthy said. "Everybody goes, 'Well, you run the West Coast offense, you run these plays, and so-and-so runs those plays,' but the footwork that this young man is being asked to do is different than he's ever had.

"It caught him on the first interception. I saw a young man get better during the course of a game running plays he hasn't played yet and doing things that I thought was exceptional for a young quarterback. So I was very pleased with his performance."

Flynn was signed after McCarthy met with reporters, so he was not around to comment on the quarterback's return. But he did say Flynn looked good in his workout in front of him and other offensive assistant coaches and personnel staff.

"A lot of the information that you need to make decisions is still coming in, so we're still trying to put it all together," McCarthy said.

One of those decisions will be whether to put Seneca Wallace on injured reserve.

A possible scenario is that the Packers could hold on to both players through the week and see if Wallace's injured groin responds to rehab enough that he could be the backup against the Giants. Then they could cut Flynn on Saturday.

They would have to create a roster spot for Flynn and with injuries to starting offensive linemen Evan Dietrich-Smith (knee) and Don Barclay (knee), cornerback Casey Hayward (hamstring), linebacker Nick Perry (ankle) and defensive end Johnny Jolly (groin), McCarthy probably would prefer to use that spot to get a position player prepared for Sunday.

McCarthy did indicate that Wallace's injury wasn't so severe he couldn't have played in an emergency against the Eagles.

"I think he would've," McCarthy said. "I think he would've because the conversation on the sideline was he wouldn't be able to move out of the pocket, and that's why we went with Scott."

If Wallace is put on injured reserve, the Packers will be on the hook for just $408,000 of his $840,000 base salary because he has a split-contract provision. He currently counts $555,000 against the salary cap due to a veteran's exemption, and that number would drop to around $430,000.

Flynn comes in with extensive knowledge of the Packers' system and would be able to play right away if needed. Some of the things the Packers are doing offensively have changed, but Flynn would be able to learn them fairly quickly.