According to the Ottawa Sun, the injury occurred during offseason training last month in Montreal.
Michalek, 27, is coming off the best season of his NHL career, when he set a career-high with 35 goals and totaled 60 points for just the second time in eight seasons. His 10 power-play goals also tied for the team lead.
He's, believe it or not, actually one of my favorite guys, and I've ended up trading him twice. I appreciate what he's done. He was one year away from being an unrestricted free agent, and I felt with this opportunity, that it was a chance that we were able to get somebody for him in Nick Bonino and Adam Clendening.
— Penguins GM Jim Rutherford on forward Brandon Sutter