Mikkelson lost an edge and went flying headfirst into the boards. He briefly lost consciousness and was removed on a gurney to Tampa General Hospital, where he was treated and released.
"I'm sore today," Mikkelson said. "I was hustling after the puck because Steven Stamkos was right behind me, and I just blew a tire. No headaches, nothing on the CAT scans, I just have never had anything like that happen to me before. I'm pretty stiff and sore today."
Mikkelson will sit out on a day-to-day basis until he is cleared to play.
"I don't have a timetable for his return," Lightning coach Guy Boucher said, "but I feel real fortunate because it wasn't pretty yesterday at practice. Headfirst into the boards, his shoulder, and he wasn't moving. It wasn't looking good, but we got lucky there."