Iowa coach Kirk Ferentz said quarterback Cade McNamara “has to play better” and “has to throw the ball more accurately.”Ferentz also said the struggling McNamara will remain the Hawkeyes’ starter as the team hosts Northwestern on Saturday afternoon in Iowa City.Iowa (4-3, 2-2 Big Ten) was blanked in the first half of a 32-20 loss at Michigan State last Saturday. McNamara passed for a meager 150 yards on an 11-for-23 day that included one touchdown and one interception.For the season, he has three games with less than 100 yards passing and only one game with more than 200 yards, totaling just 944 yards through seven games.Running back Kaleb Johnson helped keep the attack moving against Michigan State, gaining 98 yards on 14 carries, including a 75-yard TD.For the moment, Johnson’s prowess figures to serve notice to the Wildcats’ defense more than anything. He leads the conference in rushing yards (1,035) – second in FBS — and touchdowns (13).Northwestern coach David Braun said the team’s tackling suffered in spots during a 23-3 home loss to Wisconsin last week. He said that must change with Johnson up next.”This week more than ever, it’ll be critical we play with good leverage, that we tackle well,” Braun said.”It’s gonna take more than one to bring Kaleb down,” Braun added.