IOWA CITY, Iowa (AP) – Iowa running back Marcus Coker is a double major in physics and astronomy. He might have been too smart for his own good early this season.  Coach Kirk Ferentz says he thought the sophomore was over-analyzing the game and last month told him to stop thinking and start running.  Since then, Coker’s been as good as anyone in the country.  Coker has rushed for 647 yards and eight touchdowns in his last four games. He now leads the Big Ten with 1,101 yards rushing heading into Saturday’s divisional showdown between Iowa (6-3, 3-2 Big Ten) and No. 13 Michigan State (7-2, 4-1) in Iowa City.  Ferentz says going back to basics has really helped Coker break out of his early slump.