There are changes being made in the Washington Redskins' backfield that have nothing to do with broken bones.

For a second consecutive day, Coach Joe Gibbs said he did not know who his starting running back will be in Sunday's game at Pittsburgh, but will decide later in the week on John Riggins, George Rogers or Keith Griffin.

"I'm not as firm in the way I used to (be)," Gibbs said yesterday at Redskin Park. "We're working our way through it . . . they've all been productive."

For the first time in several seasons, Gibbs doesn't appear satisfied with the performance of Riggins, 36, who fumbled twice and gained just seven yards in 11 carries Monday night against the New York Giants.

Nor is he happy with George Rogers, who has had trouble hanging onto the ball this season and fumbled in the third quarter Monday night on the Redskins' first play after Riggins' second fumble. Rogers gained just 23 yards on seven carries.

So Gibbs turned to Griffin, his third-down back, for the rest of the game. Griffin, in his second pro season, gained 44 yards in 15 carries to lead the Redskins in rushing.

Gibbs liked the way Griffin played. But did he like it enough to bench two high-priced veterans who clearly are not happy with time-sharing?

Yesterday in practice, things looked the same. Riggins worked first, then Rogers, then Griffin, who is expected to get a little more practice time than usual this week.

When asked if he had a comment on the situation, Riggins simply said "No."

Rogers, however, says he is disappointed and upset by how he has played and the position he is in. He has averaged 11.5 carries per game; Riggins, 13.5.

"Right now, I feel the situation is vague," he said. "I'm in one minute, out the next. If I'm supposed to hold onto the ball, I've got to have it. I'm not making excuses, but if I played more and got the ball more, I wouldn't fumble."

Griffin realizes he is in the best position of the three, if only because he comes in as an incumbent of sorts.

"It does feel good when we're playing the Giants, in a big game, a must win, and they came to me," he said. "It seems like things are changing, that they are searching for the best combination. If they do come to me, I'd go nuts, thank God and say, 'My dream is happening.' "

Rogers says coming in cold off the bench leads to his fumbles and indecision on the field. "In order to be productive, I've got to carry the ball," he said. "When I'm on the bench, I'm not concentrating as hard as if I'd been in there."

In the 23-21 victory over New York, Rogers fumbled at the Washington 23 and the Giants recovered. Three plays later, Joe Morris scored a touchdown that gave the Giants a 21-14 lead.

After Rogers' long, slow walk to the bench, he sat down by himself. When tight end Rick Walker came over to console him, Rogers slid farther away. He never returned to the game.

"When I don't get to go back in at all, I feel like they've lost confidence in me, like they think I'm gonna do it again," he said.

Tops on the list of Gibbs' pet peeves is fumbling. He just hates fumbles.

"More than anything else," Rogers said, shaking his head.

Griffin, who fumbled often last season, walked around his townhouse in the offseason with a football under his arm. Everywhere he went, the football went along with him. He has not fumbled this season.

"That's in his favor, no doubt about it," Rogers said.

Something else is in Rogers' favor -- the future. There are those within the organization who believe Rogers should start and play most of each game. They think he will play better and they believe it certainly will help him feel better.

Gibbs said he has considered that idea, but, so far, he has not embraced it.

Already, Rogers allows himself to think of next year. "It will be a better situation as far as I'm concerned because, if John doesn't come back, it will be just two backs, not three," Rogers said.

Gibbs said one of the reasons he has not been able to make up his mind on a running back is because "there are 1,500 other things going on."

Many manifested themselves at practice yesterday.

The Redskins signed rookie wide receiver Joe Phillips, their leading receiver in preseason, as a possible replacement for Malcolm Barnwell, who was waived Tuesday. Phillips and veteran Mark McGrath apparently will battle for the No. 4 wide receiver spot. A decision will be made at the end of the week, Gibbs said.

The offensive line has changed again. At practice, right to left, it was tackle Mark May, guard Ken Huff, center Jeff Bostic, guard Russ Grimm and tackle Dan McQuaid.

Center Rick Donnalley (fractured left hand) watched practice. A decision on his status will be made later in the week.

Tackle Joe Jacoby (sprained right knee) and punter Jeff Hayes (torn right quadriceps) returned to practice, but neither did much. Jacoby remained on another field, testing his knee.

Linebacker Neal Olkewicz (torn right pectoral muscle) also watched practice, and cornerback Darrell Green left early after turning his right ankle.

Guard R.C. Thielemann, who tore a ligament in his right knee in the Chicago game, cleaned out his locker and flew to Atlanta, where he will undergo surgery Tuesday, he said. Dr. John Garrett, his team doctor with the Falcons, will perform arthroscopic surgery and see if more surgery is needed.

Thielemann, who has been on injured reserve for seven weeks, will miss the rest of the season.