The Badgers (1-3, 0-2 Big Ten) said Mertz and tight end Jake Ferguson went to the locker room with chest injuries.
Michigan’s Daxton Hill sacked Mertz on a third-and-9 play in the first series of the third quarter. Mertz was on the ground for a couple of minutes before heading to the sideline, entering the medical tent and going to the locker room.
Michigan (5-0, 2-0) was leading 13-10 at the time Mertz was injured and scored 25 straight points to put the game out of reach.
Mertz was 8-of-15 for 115 yards with a touchdown pass to Chimere Dike before getting hurt. Chase Wolf replaced Mertz and went 3-of-8 for 52 yards with a touchdown pass to Clay Cundiff and an interception.
After being ranked 12th to start the season, the Badgers have dropped three of four games and have lost eight straight games against ranked teams.
Wisconsin starting center Joe Tippmann also missed Saturday’s loss after he was poked in the eye during warm-ups.