CLEVELAND — Often overlooked and always overshadowed by their star-studded offense, the Indianapolis Colts' defense found the end zone on a day Peyton Manning couldn't.

Defensive end Robert Mathis scooped up Derek Anderson's fumble and rumbled 39 yards for a touchdown in the fourth quarter as the Colts stayed in the thick of the AFC playoff chase by winning their fifth straight, an ugly 10-6 decision over the snake-bitten Cleveland Browns on Sunday.

Mathis' big play helped bail out Manning and Indy's high-octane offense, which failed to score a TD and never got humming with its usual efficiency.

Still, the Colts (8-4) got a 30-yard field goal from Adam Vinatieri and improved to 5-0 in November, a month-long run that has allowed them to recover from a 3-4 start.

The Browns (4-8) lost their fourth straight at home and may be without quarterback Derek Anderson and tight end Kellen Winslow for an extended period.

Anderson, starting in place of the injured Brady Quinn, sprained a knee ligament in the final two minutes and is likely done for the season. Browns coach Romeo Crennel said Ken Dorsey will start next Sunday at Tennessee.

Anderson was dropping back to pass when offensive tackle Kevin Shaffer fell on him while being knocked backward by a charging Mathis. Anderson tried to get up, but couldn't and had to be helped to the sideline. Dorsey came in for the final three plays and was intercepted on the Browns' last snap.

"It's not very good," said Anderson, who will undergo more tests on Monday. "I felt a burn, a pain. It's disappointing."

Winslow went out on the first play of the third quarter with an ankle injury and didn't return. He declined interview requests following the game.

The loss of two of his best players won't help Crennel, who may be down to his final days for the Browns, who are 1-6 at home and haven't scored in nearly 135 minutes.

Manning finished 15-for-21 for 125 yards and was unable to find the same holes in Cleveland's secondary that Houston's Sage Rosenfels, Denver's Jay Cutler and Baltimore's Joe Flacco exploited in recent weeks. The Colts had only 215 total yards, ran just 50 plays and had the ball for less than 28 minutes.

But they won, and that's all that matters this time of year.

Anderson, who went 16 of 26 for 110 yards in his first start since being benched for Quinn, was setting up to throw on third down when he was hit from behind by Dwight Freeney, who bull rushed tackle Joe Thomas into his quarterback. The ball squirted loose, Mathis picked it up and lumbered in for the game's first and only TD.

Crennel's future could hang on the way the Browns finish this season. There are already rumors about the club's interest in former Pittsburgh coach Bill Cowher, but Browns owner Randy Lerner said earlier this week that he won't make a decision on Crennel or general manager Phil Savage until after the season.

Lerner denied he has made contact with Cowher, who played linebacker for the Browns for three seasons and was an assistant coach with Cleveland from 1985-88.

The Colts came in as the NFL's most efficient team inside their opponent's 20-yard line, scoring a touchdown on 72 percent of their visits and coming away with points 94 percent of the time.

But they failed to get a TD on two drives deep into Cleveland territory in the first half.

Manning fumbled trying to sneak in from the 1-yard line just before halftime. On fourth-and-goal, Manning seemed to be on his way across the goal line, but when he reached out with the ball it was knocked away by Browns safety Brodney Pool. Colts tight end Dallas Clark pounced on the ball in the end zone, but only the fumbling player is allowed to recover it for a score.

Anderson completed his first seven passes — only one longer than 5 yards — and had the Browns on the Colts 9 following a 16-yard slant pass to Braylon Edwards.

But Cleveland's longest scoring drive of the season bogged down and Phil Dawson kicked his second field goal to make it 6-3.