As much tape as they have watched of Ponder, the Steelers are actually more familiar with his backup having played against Cassel three times, including once last season.
That sample size suggests that the Vikings will rely on All-Pro running back Adrian Peterson more than ever Sunday at Wembley Stadium.
Cassel, who started the past four seasons for Kansas City before signing with Minnesota, has completed just 47.4 percent of his passes in the three starts he has made against the Steelers.
He has averaged 190.3 passing yards in those games and thrown two touchdown passes and three interceptions. Cassel is 1-2 against the Steelers in those starts, having played well against them in 2009 in beating them at Arrowhead Stadium.
History isn’t all that could benefit the Steelers from the switch the Vikings made because of the rib injury that has sidelined Ponder.
The Steelers had been worried about Ponder’s scrambling ability, and that is not as much of a concern with Cassel.
The key for the Steelers is to stop Peterson and make Cassel beat them. If they are successful in doing that the turnovers that have eluded the Steelers defense could come in London.
“There’s no question we’ve got to help our [offense],” defensive coordinator Dick LeBeau said of the Steelers not forcing a turnover through three games this season. “We’ve had the ball out. We’ve had the ball bouncing around but haven’t got it. I think we’re going to get some turnovers.”
The Vikings have already committed 10 of them, and if the Steelers can jump on them early they could force Minnesota to rely on Cassel’s right arm more than it wants.
Consider that the Steelers’ only leads this season have been 3-0 and 2-0.
“It’s tough when games are tight and you’re not putting quarterbacks in possession where there’s long yardage and they’re taking risks down the middle of the field,” strong safety Troy Polamalu said. “That’s what makes it tough getting turnovers.”