ANN ARBOR, Mich. (AP) — All season, Michigan has been able to count on its defense, even if the offense has struggled for consistency. After Saturday’s 38-31 overtime win over Northwestern, though, the 23rd-ranked Wolverines can’t even be sure about that. The Wildcats put up 431 yards against Michigan, and should have won the game in regulation if not for a bad punt and a spectacular pass from Devin Gardner to Roy Roundtree. Michigan will be facing an entirely different kind of attack Saturday in Iowa’s pro-style power-running system.