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PITTSBURGH -- Brett Favre, Adrian Peterson and the Minnesota Vikings were anything but perfect.

The Vikings couldn't gain a half-yard when it might have turned the game, then watched the Steelers' big-play defense end their unbeaten season with two long touchdown returns in the final 6½ minutes.

LaMarr Woodley's 77-yard fumble return and Keyaron Fox's 82-yard interception return on turnovers by Favre allowed the Steelers to turn back Minnesota's repeated comeback attempts, and the Steelers rode three major defensive stands to an important 27-17 victory Sunday.

The anticipated quarterback showdown between Favre and NFL passing leader Ben Roethlisberger became a defensive duel. And the Super Bowl champion Steelers (5-2) -- No. 1 defensively the last two seasons -- are tough to beat in any game that's decided by defense.

The Vikings (6-1) conceded as much in the third quarter when, after failing to score from a half-yard out on three plays in which Peterson got the ball only once, they settled for a field goal that kept Pittsburgh in the lead at 13-10.

To the Steelers, the goal-line stand was as decisive as the two defensive touchdowns that followed.

"That's the biggest point of the game," safety Ryan Clark said. "You have the best running back in the world and you don't give it to him. They're saying they can't beat us running, and that's a major statement when you have the guy they have back there."

Woodley's return, with the linebacker huffing and puffing for the final 30 yards after Brett Keisel stripped Favre of the ball, was reminiscent of James Harrison's 100-yard interception return for a touchdown in the Super Bowl against Arizona. Coach Mike Tomlin called it "one of those slow-motion moments that are a joy in this business."

The touchdown put the Steelers up 20-10 with 6:23 remaining, after the Vikings drove to the Steelers 8 and were in position to take their first lead since Peterson's 2-yard touchdown run put them up 7-3 in the second quarter.

"I got to the 40 and I didn't think I was going to make it," Woodley said.

The Vikings weren't done, not in this season of last-minute surprises. Percy Harvin answered with an 88-yard kickoff return touchdown, but Favre couldn't pull this one out after twice previously rallying the Vikings in the closing minutes.

"There were a lot of what ifs, a lot of reasons we didn't win," Favre said. "The red zone was one of them. They're physical, and they were as good as we thought they'd be. ... When I came here and looked at our schedule [and saw the Steelers game], I went, 'Oh-h-h.' "

With Favre hitting Peterson on a 29-yard pass play, the Vikings drove to the Steelers 18 with just over a minute remaining, and their biggest victory of an improbably good season awaited.

But Fox intercepted Favre's pass intended for Chester Taylor and returned it almost the length of the field, with nearly every Viking except Favre in pursuit. Favre had been intercepted only twice previously.

"Brett tried to force it in there and the running back bobbled it and slipped out of his hands and it fell into my lap," Fox said. "I had just run across the field after Peterson and I was winded, so it felt like it was 100-plus yards."

The Vikings' most significant missed opportunity came when they had the ball only a foot or so from the goal line midway through the third period. Peterson, held to 69 yards on 18 carries after averaging 161.5 yards in his first two games against AFC North teams, failed to get in on first down.

On the next two downs, Favre couldn't get the ball to covered receivers in the end zone. Coach Brad Childress then settled for Ryan Longwell's 18-yard field goal rather than go for it on fourth down, as the crowd of 65,597 -- a Steelers record at Heinz Field -- loudly cheered the potentially decisive stand.

"We had three chances," Favre said. "It's easy to look back now and say we should've done this or should've done that. I would think handing it to Adrian, he'd get it in. I'm sure he will say he should've went in, but ..."

Said Peterson, "Playing against the Pittsburgh Steelers and their defense -- I felt it's the best defense we're going to face -- you've got to get those seven points. I was highly upset about having to settle for three points."

Favre (34 of 51, 334 yards) was better statistically than Roethlisberger (14 of 26, 175 yards) -- except for the turnovers. The Vikings outgained Pittsburgh 386-259, but couldn't outscore the Steelers defense.

Game notes

Steelers DE Travis Kirschke (calf) and LB Lawrence Timmons (ankle) left with injuries during the frantic fourth quarter, after Vikings WR Bernard Berrian (left leg) was pulled. ... Minnesota had only four turnovers in its first six games. ... Pittsburgh hasn't allowed a 100-yard rusher in its last 25 regular-season games.