Dr. Arthur M. Pappas spent about a quarter-century as the team physician and part-owner of the Boston Red Sox, and in many ways he was a utility infielder in the state’s medical community — if a single ballplayer could simultaneously play first base, second, and shortstop, that is.

Two years before becoming the team’s medical director in 1978, Dr. Pappas admitted and performed surgery on the first patient at what is now UMass Memorial Medical Center. While caring for and operating on Red Sox players, he also was a professor and founding chairman of the orthopedics and physical rehabilitation department at UMass Medical School, and his philanthropy reached across the state.

Dr. Pappas, who lived in the Auburn house where he was born, died Tuesday at the medical center, according to UMass Medical School, which did not release a cause. He was 84.

His dual role as part-owner of a team whose players he treated drew criticism at times, for the potential conflict of interest, though defenders in the medical community pointed out that any doctor on a professional sports franchise’s payroll faced a similar financial conflict.

Most players were untroubled, and many athletes from other teams sought medical advice from Dr. Pappas, who was a pioneer in sports medicine and was associated with the Red Sox until about a dozen years ago.

“I don’t understand what all the criticism is about,’’ legendary Red Sox outfielder Carl Yastrzemski told the Globe in 1999, adding that his career would have ended sooner were it not for Dr. Pappas’s expertise. “This man is one hell of a doctor. He kept me on the field for the last five or six years. Without him, I couldn’t have played.’’

Dr. Pappas also filled multiple medical roles in an era before sports psychology emerged as a specialty.

“He was a part-time psychologist, too. He put us back together when we fell off the wall — Humpty Dumpty stuff,’’ former Red Sox pitcher Bruce Hurst said in an interview. “I had a very high regard for Dr. Pappas, both as a person and a physician. I really appreciated the kind of holistic approach he took to all of us.’’

In a statement, Sam Kennedy,team president, said the Red Sox “salute his contributions to sports medicine, but also the impact he made far beyond the playing fields, with the care he provided children with severe orthopedic challenges, and the many philanthropic efforts undertaken by Dr. Pappas and his wife, Martha.’’

Dr. Michael F. Collins, the chancellor of UMass Medical School, said in an interview that Dr. Pappas was “one of the vital visionaries and architects of the university’s future. He was in every way a giant of the medical school.’’

Collins added that “the public part of his life was well reported and well spoken about, but it was really the tender acts of kindness toward his many patients, many of them children, that he was always so proud of. When I would sit with him that is what he would talk about.’’

For decades, Dr. Pappas treated scores of amateur athletes whose names would never be as well-known as the Major Leaguers under his care. He was particularly renowned for rehabilitating pitchers such as Cy Young Award-winners Roger Clemens and Dennis Eckersley.

But when Worcester State College presented Dr. Pappas and his wife with a community service award in 2008, instead of telling stories about ballplayers, he spoke of restoring leg mobility to a severely disabled child who was smuggled out of Poland and through Canada to Worcester during the Cold War.

He also mentioned a patient who called him after her wedding ceremony to express thanks for his treatment, which made it possible for her to walk down the aisle.

Dr. Pappas’s accomplishments brought him considerable praise, but “I think he got way more out of giving,’’ Collins said.

“This was a man who didn’t forget where he came from, and was really a classic giving doctor.’’

The philanthropy of Dr. Pappas and his wife was particularly felt in their shared hometown of Auburn, where in 2012 the Dr. Arthur Pappas and Dr. Martha Pappas Recreation Complex opened.

The Worcester Telegram & Gazette honored the couple with its Isaiah Thomas Award for philanthropy and leadership.

“Martha was always with him,’’ Collins said. “I think they were such a proud couple together. She played a very large role in his life, and in the life of our institution.’’

One of three siblings, Arthur Michael Pappas was born in Auburn. He was a four-sport high school athlete in Auburn and lettered as a football lineman at Harvard College.

Dr. Pappas received a bachelor’s degree from Harvard in 1953 and graduated from the University of Rochester School of Medicine. For two years he served in the Navy, doing research at the National Naval Medical Center in Bethesda, Md., and he finished his medical training in Boston at Children’s, Massachusetts General, and Peter Bent Brigham hospitals.

In 1956, he married Martha Riley, who grew up in Auburn and was an athlete, too. She received a bachelor’s degree from Wellesley College, graduated from Boston University with a doctorate, and formerly was an English teacher and department chair at Lincoln-Sudbury Regional High School.

Dr. Pappas was president of the Massachusetts Amateur Sports Foundation, which sponsors the Bay State Games; a member of the sports medicine committee of the American Academy of Pediatrics; and chairman of the Board of Trustees at Massachusetts Hospital School in Canton, which provides treatment and services for children and young adults with multiple disabilities.

Among the many honors Dr. Pappas received were lifetime achievement awards from the Massachusetts Medical Society and the Massachusetts Hospital School, and an honorary degree from UMass Medical School, where a chair in orthopedics was established in his name.

The family will hold a private service for Dr. Pappas, whose wife is his only immediate survivor.

A public celebration of his life and career will be announced.

After Red Sox owner Tom Yawkey died in 1976, Buddy LeRoux asked Dr. Pappas to join a group that was formed to buy the team, and to purchase a limited-partner share for about $1 million. At the time, Dr. Pappas was an orthopedic surgeon with a national reputation for devising programs for developmentally disabled children. He had been director of Family Health Services for the state Department of Public Health, and during his tenure, Massachusetts became a national leader in providing services to handicapped children by expanding programs and facilities.

During Dr. Pappas’s tenure with the Red Sox, critics of his multiple roles as team physician and part-owner included Nomar Garciaparra. In the mid-1990s, Red Sox second baseman Marty Barrett was awarded $1.7 million after suing Dr. Pappas, claiming that a knee injury had been misdiagnosed.

Among those who supported Dr. Pappas was Dan Duquette, who was then general manager of the Red Sox and noted that players from other Major League teams regularly sought medical advice from him. “It is well known that Dr. Pappas is considered one of the top physicians in baseball,’’ Duquette told the Globe in 1999.

By that year, even Barrett was telling the Globe “I respect Dr. Pappas,’’ and adding that “he did a lot of things for my family and children and helped them . . . I think he’s a great man.’’

Steve Lyons, a former Red Sox player who is now a sportscaster at NESN, recalled that Dr. Pappas “performed a foot surgery for me my rookie year, and I never had a problem with it again.’’

Dr. Pappas, Lyons recalled, could be found at the outfield end of the Red Sox dugout for home games, even when work didn’t require his presence.

“He was always right there with a big smile and those bushy eyebrows,’’ Lyons said.

Bryan Marquard can be reached at bryan.marquard@globe.com.