He fractured a vertebra against Windsor:
Michigan defenseman Jon Merrill suffered a slight neck fracture during the team's exhibition game with Windsor on Tuesday, and will miss approximately six weeks, according to NorthJersey.com's New Jersey Devils blog.
Merrill's NHL rights are held by the New Jersey Devils. The blog post was quoting Devils general manager Lou Lamoriello, who said he spoke to Merrill.
Merrill was injured on a hit from behind into the boards during Tuesday's game.
“It’s nothing that needs surgery,” Lamoriello was quoted as saying. “It’s just needs time to heal. But I spoke to him today and he’s doing fine.”
That's not good, and means that all of the Serville/Clare/Chiasson group will skate until he's back.