Sources: Jay Cutler has broken thumb

CHICAGO -- Chicago Bears quarterback Jay Cutler broke the thumb on his throwing hand during Sunday's 31-20 win over the San Diego Chargers, according to sources familiar with the situation, and the injury likely will keep him out for the final six games of the regular season.

Cutler plans to undergo further evaluation of the injury on Monday, but the injury will require surgery that will keep him out "at least the rest of the regular season," the sources said.

A team spokesman wouldn't confirm Cutler's injury.

With six games left on the schedule, the team is hopeful Cutler can return for the postseason, should the Bears advance.

Cutler completed 18 of 31 passes for 286 yards and two touchdowns Sunday, and avoided a sack for just the second time in his past 30 games. According to ESPN Stats & Information, Cutler completed six of eight attempts under duress, including a third-quarter touchdown to Johnny Knox.

Under pressure, the quarterback produced a passer rating of 154.7 against the Chargers, which is interesting considering Cutler had attempted 81 passes under duress -- the most in the NFL -- for a passer rating of just 67.0 in the nine games headed into Sunday.

Cutler might have suffered the injury on a fourth-quarter interception to Antoine Cason on a pass intended for Knox, who slipped, essentially causing the turnover. In the attempt to make the tackle on Cason's 64-yard return, Cutler suffered the injury.

So the news of the quarterback's broken right thumb puts a damper on a red-hot outing that Bears coach Lovie Smith called "outstanding."

Cutler finished the game, completing his final two passes for 24 yards in the team's final drive.

With Cutler expected to miss time, the attention turns to backup Caleb Hanie, who will take over as the starter. A fourth-year veteran, Hanie played in two games in 2010, completing 8 of 14 passes for 66 yards and an interception.

Hanie also filled in for Cutler in the NFC title game, and hit 13-of-20 for 153 yards a touchdown and two interceptions in a loss to the Green Bay Packers.

Rookie Nathan Enderle is the only other healthy quarterback on the roster, which means there's a good chance the Bears plan on making an acquisition at the position. It's expected the Bears would consider quarterbacks with experience playing in the system of offensive coordinator Mike Martz.

Former Jaguars quarterback David Garrard -- with no experience in Martz's system -- seemed like a logical option, but he's just starting rehabilitation from back surgery and won't be able to undergo any contact for at least three weeks, according to a source.

Michael C. Wright and Jeff Dickerson cover the Bears for ESPNChicago.com and ESPN 1000.