FOXBOROUGH, Mass. -- Little-known BenJarvus Green-Ellis gave the Patriots a boost in the tight AFC East race.
And he helped hand the free-falling Buffalo Bills a costly loss.
The undrafted rookie from Mississippi rushed for a career-high 105 yards and scored a touchdown for the fourth straight game and New England's defense dominated in the second half for a 20-10 win on Sunday.
Green-Ellis began the season on the practice squad but is the Patriots' top runner with Laurence Maroney on injured reserve and Sammy Morris missing the last three games and LaMont Jordan out for the last five.
"Wherever we are on the field, I just try to get it to the end zone," Green-Ellis said. "That's my job every play."
He capped a 19-play drive with a 1-yard touchdown with 1:57 left long after Matt Cassel rushed for a 13-yard touchdown on the Patriots' first series. It's the longest touchdown run by any Patriot this season.
Cassel, the steadily improving replacement for Tom Brady, directed the offense with poise and completed 23 of 34 passes for 234 yards.
The defense held the Bills to 58 yards in the second half -- while the offense piled up 192. The Patriots had the only two interceptions of the game and outgained the Bills 370-168.
"When you don't allow big plays, it definitely keeps control of the game in your favor," cornerback Ellis Hobbs said.
The Patriots (6-3) moved a game ahead of the Bills (5-4), who are 1-4 since winning their first four games. The New York Jets routed St. Louis 47-3 and remained tied with New England. Miami (5-4) beat Seattle.
"We realized this was a big pivotal game," Bills linebacker Paul Posluszny said. "We have to get a winning feeling and we don't have that now."
The loss -- Buffalo's 10th straight to New England -- was especially harmful since the Bills had lost their previous two games against the Dolphins and Jets and dropped to 0-3 in division games. The Patriots are 2-1 against AFC East opponents and face the Jets and Dolphins in their next two games.
"It's getting down to crunch time now," Patriots linebacker Tedy Bruschi said.
That was hardly enough against a strong defense.
"I'm frustrated. We watched the film and I knew what they would do," Edwards said. "But watching it on tape and them performing is completely different."
The Patriots took receiver Lee Evans out of the game by playing their safeties deep.
"We beat up their receivers and, for the most part, stopped the running game," safety James Sanders said.
The Patriots scored their first touchdown with help from a 21-yard completion to Wes Welker that moved the ball to the Bills 17. Welker appeared to land with only one foot inbounds before Cassel ran up the middle to score two plays later.
New England stretched the lead to 10-0 on Stephen Gostkowski's 32-yard field goal early in the second quarter. The Bills made it 10-3 on the next series on a 24-yard field goal by Rian Lindell after they reached a second-and-goal at the 4-yard line but lost 3 yards on the next two plays. Then Gostkowski missed a 48-yarder, ending his streak of 10 successful field goal attempts.
But he connected for a 37-yarder on the first series of the third quarter, giving the Patriots a 13-3 lead. Then the defense really clamped down.
On their first series of the third quarter, the Bills punted. Their next possession ended in an interception by Deltha O'Neal. The Patriots couldn't capitalize and lost the ball when Cassel's fumble was recovered by safety George Wilson.
Buffalo moved to a second-and-5 at the New England 36 but Ty Warren sacked Edwards for a 6-yard loss and Edwards threw an incompletion, forcing Buffalo to punt.
The 19-play drive tied the Patriots record for most plays in one series. They also did it on Sept. 15, 2002 against the New York Jets.
"I didn't even know it was 19 plays," Green-Ellis said. "Nobody in the huddle was tired. Everybody was relaxed and just concentrated on what we had to do."
Welker set an NFL record with at least six catches in each of the first nine games of the season, breaking a tie with Jimmy Smith. Welker had 10 catches for 107 yards. ... Evans had just two catches for 22 yards and Marshawn Lynch gained only 46 yards on 14 carries. ... The Bills played without two of their top defensive players. Safety Donte Whitner was sidelined after separating his shoulder last week in a loss to the Jets. And pass rusher Aaron Schobel missed his fourth straight game with a foot injury.