I didn't think so. I mean, I suppose he could have been HIV positive, but it's tough to say that impacted his play (see numbers below). Also, it's not an injury. Bill Simmons felt the need to throw his "injury" into his on-the-fly list of the 10 biggest playoff injuries in the past 25 years:
(The 10 biggest playoff injuries of the past 25 years, in no particular order: Manu in '08; Isiah in '88; McHale and Walton in '87; D-Wade in '05; Duncan in '00; Malone in '04; Worthy in '83; Pippen in '98; Magic in '91; Doc Rivers in '94. All of those injuries potentially swung the Finals except for Pippen's back injury in '98 -- that was the year when Pippen played at 50 percent and MJ said, "Screw it, we're winning anyway.")
I don’t recall Magic being injured in the 1991 playoffs. In the 1991 finals, Magic Johnson played 43, 43, 50 (OT), 44, and 48 minutes. In the 1991 playoffs, Magic averaged 43.3 minutes, 21.8 points, 12.6 assists and 8.1 rebounds per game. That’s, you know, pretty good.