An associate professor at the Medical School has emerged at the center of a controversy over conflicting diagnoses of Boston Celtics basketball star Reggie Lewis, who died suddenly Tuesday night at the age of 27.

The professor, Dr. Gilbert H. Mudge Jr., cleared Lewis to play earlier this spring because he said the basketball player had a mild nerve disorder. Mudge's diagnosis came after a team of 12 doctors at New England Baptist Hospital--dubbed "The Dream Team" by Celtics officials--said Lewis had a heart condition and should quit playing basketball.

Mudge, who is also a cardiologist at the Harvard-affiliated Brigham and Women's Hospital, is a regular instructor in the course, "Clinical Cardiology." He is scheduled to teach it again during the 1993-94 academic year. According to the medical school, Mudge also will teach "Core Medicine Clerkship I" next year.

Nicknamed Punky, Mudge is credited with founding an exchange program between a Moscow hospital and Brigham and Women's.

Mudge's diagnosis has been criticized by local doctors and the press. Globe columnist Dan Shaughnessy tore into Mudge in a front page column Wednesday for the doctor's diagnosis and his smug demeanor during a press conference to discuss Lewis' condition in May.

The Celtics team physician, Dr. Arnold Scheller, also appeared to criticize the doctor during a press conference yesterday.

Boston police said this week they are maintaining a constant "presence" at Mudge's home. He has not been seen in public, has received death threats and his only public statement was a "no comment" to the Associated Press earlier this week.

The Boston Globe disclosed yesterday that while Lewis accepted Mudge's diagnosis initially, he appeared to experience doubts in the weeks shortly before his death.

The Globe reported that Lewis flew to Los Angeles for a third opinion and that one of the doctors he consulted, Dr. William G. Stevenson of UCLA Medical Center, agreed with Mudge's diagnosis.

Lewis also had received warning signs from a heart monitor he was wearing when he exercised, the Globe reported.

State officials said yesterday that Mudge has had no successful malpractice complains filed against him