LONDON - The Minnesota Vikings aren't just playing in a different country on Sunday, they're also starting a different quarterback.

Matt Cassel will get the start in place of injured Christian Ponder. The Vikings play the Steelers at Wembley Stadium in London.

Both teams are looking for their first win.

Trying to avoid its first 0-4 start in 45 years, Pittsburgh is hoping its defense can spark a turnaround.

"Steelers football has always been about the defense, about going out there and dominating, getting turnovers, and putting points on the board regardless of what the offense does," linebacker LaMarr Woodley said. "We know what we're dealing with a guy like Adrian Peterson. We just can't give up the big plays."

With the Vikings also 0-3, Peterson will be expected to carry the load on Sunday with quarterback Christian Ponder out with a fractured rib.

Ponder, who ranks 30th in the NFL in passer rating (65.9), suffered the injury in the second quarter of last weekend's loss to the Cleveland Browns and struggled with accuracy late. He underwent a CT scan Monday that revealed the fracture, but tried to practice the past two days.

"He's a tough, tough guy, but it probably wouldn't be wise to put him in that situation," Frazier told reporters. "We have complete confidence that Matt will do a good job, our players are going to support him and he'll be the guy that will be leading us to victory on Sunday evening."

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