From the Free Press:

"We're having further tests," general manager Ken Holland said. "We're being cautious. We don't think it's anything serious. But I don't think he's going to be on the ice this weekend. Doctors aren't working (over the weekend) -- he's got to see a doctor, or get somebody to look at the results. We're hoping to know Monday whether he's cleared, or where we are."

Hopefully, it's just something minor.

Also, kind of old news:
Red Wings forward Greg Johnson did not pass his physical and may not join his teammates on ice before Monday
The Wings signed Johnson, 35, to a one-year deal worth $500,000 over the summer. The plan is to have him center the fourth line, and also to use the speedy forward to help kill penalties.

Abnormal heart test sits Johnson

From the Free Press.