SAN FRANCISCO - One play doesn't usually win or lose a game, but one play can certainly change the tide.

Nick Collins' interception late in the third quarter on Sunday in San Francisco was that play for the Packers in their 30-19 victory at Monster Park.

Green Bay's defense was on its heels a bit, having surrendered a touchdown drive to open the second half as the 49ers pulled within 17-13.

The defense had just stopped one San Francisco possession that began near midfield and was being called upon to stop another after the Packers were pinned inside their own 10 and failed to get a first down.

With the 49ers facing third-and-2 from the Green Bay 41, San Francisco quarterback Alex Smith ran a play fake and rolled to his right. Tight end Vernon Davis came off the line and was running a flag route to the far sideline.

The timing of Smith's release appeared to be off, and Collins stepped up in front of Davis, dove and made the interception with 3:54 left in the third quarter. The lead was safe, and the game was about to change.

"He was open, the quarterback had the right read, but the pressure we were putting on the quarterback gave me time to get over to undercut him," Collins said. "That was the turnaround in the game right there."

Two plays later, the Packers capitalized. Brett Favre lofted a high throw down the right side of the field to Donald Driver, who made the catch, shook a shoestring tackle attempt by Mark Roman, and outran three other San Francisco defenders for a 68-yard touchdown and a 24-13 lead.

A huge swing in three plays, to say the least.

"When you get a pick like that, you know you have to go in and score," Driver said. "Our goal was to make sure we didn't give up what we did last week. We had a couple turnovers we didn't score off of, so we knew we had to score this time."

The sequence of events seemed to energize the defense as well. On San Francisco's next possession, running back Frank Gore was stopped by Colin Cole for a 2-yard loss on second down, and then Aaron Kampman and Cullen Jenkins broke through to sack Smith on third down, forcing a punt.

The offense once again took advantage, driving 32 yards to set up a 44-yard field goal by Dave Rayner that extended the lead to two touchdowns at 27-13.

{sportsad300}The Packers kept the momentum until they stretched the margin to three scores by getting another defensive stop, a 40-yard punt return by Charles Woodson and another field goal for a 30-13 lead.

The defense then got its third takeaway of the game when A.J. Hawk intercepted Smith in the end zone with 7:31 left, erasing what little doubt remained.

But the game was certainly in doubt with the 49ers just 41 yards away from the go-ahead score in the third quarter. It was thanks to Collins that San Francisco never got another chance like that.

"An interception like that when a team might put a little drive together gets the momentum back in our favor and keeps us rolling," Hawk said. "I think the offense responded great today when we got the turnovers, and they didn't turn the ball over themselves, so that's a great way to win a game."