Bob Rydze, the U.S. team's diving coach, said today that Soviet diver Sergei Chalibashvili had barely avoided disaster several times in practice last week and shouldn't have attempted the reverse dive that ended in tragedy Saturday night at the World University Games.

Chalibashvili's condition deteriorated to very critical overnight, and today he was in a coma and being kept alive by a respirator at the University of Alberta Hospital. He suffered multiple skull fractures and lacerations when the back of his head hit the 33-foot-high hardwood platform.

Doctors said that Chalibashvili, 22, has very likely suffered permanent brain damage as a result of the injury.

After seeing Chalibashvili's head come so close to the platform a number of times in practice, Rydze left the diving area Saturday when the Soviet athlete lined up for a reverse, 3 1/2 somersault.

"I saw him do it about four or five times earlier in the week," Rydze said in an interview this morning. "I wouldn't watch. I just felt there was a good chance he would hit the platform. I went back into the training room, but there was a television set on back there, so I just put my hands over my ears. We knew it might happen.

"We were leaving the area all week when he was practicing," Rydze continued. "One time, he was so close it scared the hell out of me. He was short on the dive all week, and, in a meet, you're going to stand it up a bit, anyway. But there was no room for him to stand up. There was no question, in my mind, that he shouldn't have been doing the dive. He just didn't have the talent.

"Heck, it was obvious to me. They (the Soviet diving coaches) knew what was going on; they had to. I think, in their hearts, they must have known. The last two days, the Russian coaches were telling him he was getting too close. But as I understand it, he was under somebody else's instructions to do the dive."

A reporter from Tass, the official Soviet news agency, confirmed that Chalibashvili's mother has served as his diving coach.

Rydze, the coach at the University of Iowa, was asked why he didn't emphasize to the Soviet coaches how close Chalibashvili was to potential danger.

"It would have been tough, for us as Americans, to go up and tell the Russian coaches about something going on with one of their athletes," Rydze said. "It would look like we were trying to interfere in their business. I thought he might hit, but divers have hit the platform before. My brother hit his head in 1972 and got some stitches, but wasn't hurt seriously. In my wildest imagination, I never dreamed he'd hit as hard as he did."

Vladimir Vasin, the U.S.S.R diving coach, could not be reached for comment early today.

Genrich Khackkavanyan, a Tass reporter, said Chalibashvili had performed the dive several times in the Soviet Union, including at an international competition last March in Minsk, where he finished fourth. "He has done it very easily in Moscow," Khackkavanyan said.

A Soviet diver from Chalibashvili's hometown of Tbilisi (the capital of Georgia), was contacted by reporters, but burst into tears and refused to discuss details about her friend and diving mate.

After being pulled from the pool Saturday at about 7 p.m. EDT, Chalibashvili was rushed to the hospital a few blocks away. Dr. John Read, vice president of the hospital's medical staff, said Soviet officials have indicated they are satisfied with the procedures that took place during the ride between the aquatic center and the hospital.

Read said Chalibashvili is being attended around the clock by two neurosurgeons and an ear, nose and throat specialist from the hospital, and by a team of Soviet physicians and officials. Read said the Soviet officials asked him to be their spokesman. The neurosurgeons performed a 40-minute operation late Saturday to relief pressure on the brain.

Read said there was no "critical period as such," and that about the only thing that can be done now is to "wait and observe how his body deals with his injuries."