WATFORD, England — Minnesota Vikings quarterback Christian Ponder’s playing status for Sunday’s NFL game in London against the Pittsburgh Steelers is in doubt because of a rib injury.

Vikings coach Leslie Frazier said that practice on Wednesday will “be a big signal in what direction we’ll have to go,” with a decision expected by Friday.

“He’s fighting through a little pain,” Frazier said at the team’s base outside London. “We’re going to see how he does in practice. He’ll be limited today and we’ll talk (Thursday), but the fact he was able to finish the game (against Cleveland) was a good sign for us.

“Hopefully, there won’t be any long-term effects.”

Backup quarterback Matt Cassell is ready to step in if Ponder, who was injured early in Sunday’s 31-27 loss to the Browns, is ruled out of the game at Wembley Stadium.

“My mindset is we’re going to push it to the limit and see what we can do, in a smart way. But I’m doing everything I can to play this game,” Ponder said. “We’re going to do what’s best for the team. If I can’t do my regular duties, then Matt’s going to step in and play.”

Ponder has been under pressure since the loss to the Browns dropped the Vikings to 0-3. The third-year quarterback has thrown five interceptions and two touchdowns for a 65.9 passing rating. He has also lost two fumbles.

“My confidence hasn’t wavered,” said Ponder, who led the Vikings to the playoffs last season. “I have a great support staff around me with Adrian Peterson and the staff around me.”

Peterson said he was always ready to give Ponder a pep talk, as he did when fans at Mall of America Field began jeering the quarterback during the Cleveland loss.

“He’s bouncing back,” the Vikings running back said Wednesday. “I told him, ‘You know the business. You know how it goes. Just stay focused and continue to work. You know what to do.'”

Frazier said defensive backs Chris Cook (groin) and A.J. Jefferson (ankle) would sit out Wednesday’s practice, but safety Jamarca Sanford (hamstring) would take part.

The Steelers are also 0-3 going into the first of two NFL International Series games to be played in London this season.