Guard Kevin Grevey of the Washington Bullets said yesterday that he will not be able to run, work out or play basketball until October at the earliest because of a torn stomach muscle that was originally suffered in a game nine days before the end of last season.

"They (the Bullets' doctors) originally didn't diagnose it (the injury) as that (a pulled stomach muscle)," Grevey said. "They first called it an inflamed testicle cord."

John Lally, the Bullets trainer, said Grevey was healthy the last time he had seen him--at the end of the playoffs in May.

"I would assume he had to hurt it again someplace else after he left here," Lally said. "When he left town (following the season), he was relatively healthy. We can't diagnose pain. He played in the playoffs, didn't he?"

Grevey said during the playoffs team doctors told him he had a pulled abdominal muscle. In late May, Grevey visited Dr. Jeffrey Minkoff, physician for the Cosmos soccer team, in Manhattan and received a different diagnosis.

"He told me that two Cosmos had suffered the injury and one had his career ended and the other was out 14 months," said Grevey. "Their muscles were torn more severely than mine was, though. He (Dr. Minkoff) told me not do anything until October," Grevey said.

"That (discovering an injury to be more serious than originally thought) happens all the time," said General Manager Bob Ferry of the Bullets. "The original diagnosis could only be diagnosed by pain. It was just a bigger pull . . . (than first believed).

"It might take him a longer time to recover now, but that's something he has to deal with," added Ferry.

A team doctor, Stephen Haas, would not speak with a reporter. But, speaking through Lally, Haas said he had diagnosed the injury when it had occurred and found a strained abdominal muscle. The doctor also said he had not seen Grevey since the end of the season.

Grevey said he did not practice for the rest of the season once he incurred the injury April 9 in a game at Chicago. He missed the next three games before rejoining the Bullets for their stretch drive.

"As injured as it was, I still played," said Grevey. "I've had hamstring pulls and other injuries, but nothing has ever lagged on this long. It's very frustrating."

Despite undergoing 1 1/2 hours of rehabilitation at the National Hospital for Orthopedics and Rehabilitation every weekday, Grevey said that the injury "has not gotten much better. It will just take a lot of time. You do what you have to do."

About Grevey's having sought another medical opinion, Lally said, "Everyone has his opinions. If you look long enough, you're going to find someone who agrees with you."

Grevey said he is hoping to be ready by the early part of next season, which begins at the end of October. For the summer, though, he will just have to sit and wait.

Meanwhile, power forward Steve Lingenfelter, a second-round draft choice in 1981 who played in Italy last season, signed a contract with the Bullets yesterday. Lingenfelter, from South Dakota State, did not sign last year with the Bullets because of a disagreement over money.

According to Ferry, Lingenfelter received about the same amount this year he would have received last year. Lingenfelter said the competition was good in Italy but the coaching was not, prompting him to try the National Basketball Association.