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ST. LOUIS -- The Buffalo Bills are 4-0 for the first time in 16 years. Unlike the previous two weeks, there was no need for late-game heroics to keep them unbeaten.

Jabari Greer's 33-yard interception return on the first play of the fourth quarter was the go-ahead score in an 18-point fourth-quarter that finished off the surprisingly competitive, go-for-broke St. Louis Rams 31-14 on Sunday.

"We knew they could beat us, and we were pretty certain we could beat them, too," Bills coach Dick Jauron said. "We just ended up making more plays at the end, and that's what this game is all about. So there it is."

After three blowout losses to open the season and amid rumors he might be fired during the team's bye week, Rams coach Scott Linehan benched quarterback Marc Bulger in favor of 38-year-old Trent Green. Linehan had six new starters in all, four on defense.

The shakeup worked for a while, with rookie wide receiver Donnie Avery scoring on a 37-yard pitch and a defense led by revived Leonard Little sacking Trent Edwards four times in the first half. Linehan wouldn't commit to another start for Green, at Washington on Oct. 12 in the first game after the bye.

"I think we wanted to come out and be aggressive," Linehan said. "What did we have to lose? Come out, freewheel and go for it. I liked how that went in the first half."

The Bills' first defensive score of the year -- also Greer's first career touchdown -- came off an overthrown pass on second-and-12. It signaled an end to the Rams' fun and games while handing St. Louis (0-4) its 17th loss in the last 20 games.

"It was crucial," Greer said. "I was excited I was able to make a play that could give us the momentum."

Green blamed miscommunication between he and Torry Holt, the intended receiver on the play. Holt is the Rams' only wide receiver Green has not thrown to much.

"Unfortunately, that came back to bite me," Green said. "Unfortunately, that kind of snowballed things in the fourth quarter, and that weighs heavily on me."

Buffalo drove 81 yards on its next possession, capped by Lee Evans' 39-yard reception and conversion catch for a 28-14 cushion.

The Bills are 4-0 for the first time since 1992, the middle of its dominant AFC years. The Bills have gotten an early jump on the franchise's second winning season since 1999. But the previous two wins were nailbiters by a total of five points.

"It's not easy being 4-0," owner Ralph Wilson said after visiting the victorious locker room. "It's not easy being 1-0 in this league."

Steven Jackson had 110 yards on 24 carries, the first 100-yard rushing game the Bills have allowed any team this season, and five catches for 78 yards. Jackson's 29-yard scoring run early in the second quarter was the high point for the Rams, putting them ahead 14-6. His exuberance got the best of him when he climbed into the stands and then took his helmet off in the end zone to draw an unsportsmanlike conduct penalty.

Jackson had criticized Linehan's decision to bench Bulger during his weekly radio show.

Linehan, 11-25 in his third season, last week was put on notice to make immediate improvements by owner Chip Rosenbloom and he pulled out all the stops. The Rams took their first lead of the season on Avery's 37-yard run off a pitch from Green, his first carry of the year.

In the first half alone, the Rams also called an end-around and an option pass, both by Dante Hall to some success. They also went for it on fourth-and-3 from the Buffalo 42 late in the half, but had an incomplete pass.

Linehan said he wasn't concerned that this might have been his final game.

"I'm going to continue to do the best I can, OK, and that's the only thing I can control," Linehan said. "That's what I've done my whole life and that's what I'm going to do the rest of my life."

Buffalo mustered only 96 yards in the first half, going 1-for-7 on third down, and was held to a pair of field goals by Rian Lindell. Edwards finished 15-for-25 for 197 yards with a touchdown and an interception.

Green made his first start since Oct. 7, 2007, when he landed on injured reserve with the Dolphins after his second severe concussion in two seasons. He was 17-for-32 for 236 yards and led the Rams to a season-best 380 yards.

Game notes

Holt had four receptions for 65 yards and has 820 for his career, passing Steve Largent for 16th place. ... Rams K Josh Brown missed his first kick in six attempts this season, a 51-yarder that was wide right in the third quarter. ... Rams WR Dane Looker sustained a concussion and lost a fumble on a big hit from Leodis McKelvin after a 30-yard catch in the fourth quarter. ... Bulger was the only active Ram who did not play and escaped the Edwards Jones Dome via the visitor's locker room without speaking to reporters. ... Bills CB Terrence McGee sprained a knee.