ARLINGTON, Texas -- Dallas Cowboys Pro Bowl right guard Zack Martin suffered a hyperextended left knee during Saturday's preseason loss to the Cincinnati Bengals, a source told ESPN.

An MRI taken Sunday confirmed the hyperextension and also revealed a bone bruise, a source told ESPN's Dan Graziano. Martin is expected to be ready in time for the start of the regular season, the source told Graziano.

Martin suffered the injury in the second quarter, when Bengals cornerback Dre Kirkpatrick went low and saw his helmet hit Martin in the knee. Martin got up slowly and limped to the sideline. He did not return to the game.

In the fourth quarter, he was standing on the sideline.

"I'm not thinking that Zack is problematic here," Cowboys owner and general manager Jerry Jones said after the game.

Coach Jason Garrett said the team's medical staff was "somewhat optimistic based on the initial observation."