Greg Pratt, the starting fullback for the highly regarded Auburn University football team, collapsed after running sprints in 99-degree heat at an afternoon practice today and died at a local hospital a few hours later after his heart stopped.

An autopsy was scheduled.

School officials said Pratt, 5-feet-8 and 211 pounds, had a weight problem last season, although he had slimmed down in the spring. At one point last year, he was taken to a hospital after being unable to complete a similar drill, according to Auburn Coach Pat Dye, who said the diagnosis was heat-related problems. Today's temperature was the hottest of the year here.

Pratt, 20, a junior from Albany, Ga., had passed a physical examination at 8 o'clock this morning, a school spokesman said.

Less than five hours later, he was running 440s as part of a routine drill on the first day of practice for varsity players when he began complaining of cramps and collapsed, according to Jon Williams, the Lee County coroner.

Pratt had completed the last of three 440s, but was having trouble at the end of it, according to Dave Housel, an athletic department spokesman. Trainers took Pratt to Memorial Coliseum, where he was placed in a shower in an attempt to cool him down, Dye said.

But Pratt collapsed and paramedics were called when trainers and coaches were unable to revive him. Paramedics arrived, but Pratt already had stopped breathing. The rescue workers attempted to revive Pratt, and Dye said he believed they were able to start his heart beating "a few times," but could not produce a steady pulse.

Doctors at the hospital worked on Pratt for about two hours before pronouncing him dead.

Auburn is ranked No. 1 by a number of football publications this preseason.

Pratt transferred to Auburn after completing his freshman season at Tennessee State in 1980. After sitting out the 1981 season as a transfer, last season he started two games as a walk-on and gained 106 yards in 31 carries out of Auburn's wishbone offense.

Pratt was considered the No. 1 fullback at the end of spring training after gaining 109 yards in 22 carries in the Orange-Blue spring game. Tom Agee, the player he beat out for the position, is expected to become the starter.

"There's no question that this is a tragedy to his family; our prayers and our sympathy go out to them," a teary-eyed Dye said. "It is a tragedy to Auburn University and our football team.

"He was a fine young man in every respect and a credit to his family, the community and Auburn University. We sure will miss him. It was a very sad time for all of us."

About 50 players, many weeping openly, went to the hospital. Dye spoke to team members after he returned from the hospital.

David Housel, sports information director, said Dye and the players prayed, then the players "each went off to be by themselves or with friends."

Rusty Dean, counselor for the athletic dorm, said Pratt was a "perfect citizen who was always a positive influence in the dorm. He was a good person you couldn't help but like."

Pratt is the third Auburn player to die in the past two years, but the first to die on the field. Alan Manley, also from Albany, and Cary Condray of Birmingham were killed in an automobile accident in November 1981 while returning from Florida. Manley was Dye's first signee as Tiger coach.