The Washington Redskins, who must drop 15 players this afternoon, expect tight end Clint Didier and middle linebacker Neal Olkewicz to miss "three to four weeks" and offensive tackle Mark May to miss four to six weeks, Coach Joe Gibbs said last night.

The Redskins might have as many as six starters missing from Sunday's regular-season opener with Philadelphia because of injuries: those three plus defensive end Dexter Manley, running back George Rogers and cornerback Tim Morrison.

Manley, who partially tore the medial collateral ligament in his right knee Aug. 8, will "gradually" work himself back into practice, Gibbs said at Redskin Park, where he and his coaches met late into the night to decide whom to cut, whom to place on injured reserve and whom to keep. The final 45-man roster must be declared today, although changes undoubtedly will be made as the team reassesses its injuries.

Gibbs said Manley will begin some one-on-one drills with pads this week. Manley likely would need a week of full contact once he got back into a normal practice routine before he could play, which means he probably won't be available this week for the Redskins-Eagles game at 1 p.m. at RFK Stadium.

"I think it's hard to count on him," Gibbs said.

Gibbs said Rogers, who has had a sprained left big toe for more than a month, will be evaluated in practice. The team might not know if he will be available for the first game until "the last minute," Gibbs said. If Rogers can't start, Keith Griffin would start and share time with rookie Timmy Smith, Gibbs said.

May, hurt in the Redskins' 26-14 victory over the Los Angeles Rams Saturday night, is expected to miss as much time as Manley because their injuries are similar. Without May, the Redskins will start 300-pound rookie Ed Simmons, who must face Reggie White, the Eagles' Pro Bowl defensive end.

"There's not a lot you can do," Gibbs said. "{Simmons is} going to have to play. He's played real good in preseason for us. He's been up against other good players from other teams, although Reggie White is exceptional. I think we'll just have to count on Ed doing a good job."

May is a strong candidate for injured reserve, but there are two ways he can be placed on it. If he goes on injured reserve today (preseason), he must miss at least six weeks. The Redskins have up to three "free" moves off injured reserve from preseason and a total of eight "free" moves for the entire season, not counting the playoffs. A "free" move is one that can be made without requiring that the player be placed on waivers.

Obviously, the Redskins will place on injured reserve only those starters and key players who have injuries that will take four weeks or longer to heal. Olkewicz, who had cartilage removed from his right knee Aug. 16, is a question mark for injured reserve because he could be back in less than four weeks.

Other candidates for injured reserve would be three players injured Saturday night at Anaheim Stadium: wide receivers Clarence Verdin (pulled right hamstring) and Derek Holloway (sprained right big toe) and third-string quarterback Mark Rypien (sprained back).

"You've got so many variables to consider," Gibbs said. "The guys who are hurt, how many guys you want to count {on the 45-man roster}. . . . I mean it's really a nightmare this time trying to figure who to do what with."

The tight end situation, confused by Didier's pulled left hamstring and Terry Orr's badly bruised left shoulder, is one that has Gibbs and has staff confounded. It appears Glenn Dennison has won some of the coaches' confidence at H-back with his receiving and blocking (he took out two Rams with one block on one of Smith's receptions). Don Warren is the starting blocking tight end, of course, and Chris Dressel looks like his backup. But will the Redskins keep Didier and/or Orr on the active roster and only three other tight ends, or put Didier and/or Orr on injured reserve and keep four?

Gibbs acknowledged that "for the first time," he is considering keeping only three tight ends.

"I was upset we had that many guys hurt again," he said immediately after the game. "We've kind of been accumulating injury after injury, which is going to take a guts effort next week and is really complicating the picture on our team, the makeup of our team, and what to do about the final selections."

Perhaps the most interesting decisions will be made in the defensive backfield. Eleven safeties and cornerbacks are on the roster, and the team might keep as few as seven, as many as nine.

"Seven would make it a real tough decision," said defensive backs assistant Emmitt Thomas. "If Coach Gibbs gives us eight or nine, we'll be okay."

Look for at least two rookie defensive backs to make the team: top draft pick Brian Davis and eighth-round choice Clarence Vaughn. They entered the game early, Davis in the team's second defensive series, Vaughn in the fourth. They played much of the rest of the game; Davis worked at left cornerback, Vaughn at strong safety.

Davis was beaten by Ron Brown on a comeback route for a 24-yard catch in the first quarter, but then played well, Thomas said.

"He lost his technique a little bit on the comeback, but we talked to him on the phone and then he settled down and I thought he played super," Thomas said.

Vaughn, said Thomas, was "exceptional."

"He played a good game, made some good hits, made a key interception," Thomas said.

Vaughn's leaping interception of Hugh Millen in the fourth quarter came one play after Vaughn began signaling his coaches to take him out of the game. On a Washington kickoff at the end of the third quarter, Vaughn hit his head. "I started losing my eyesight, getting blurry out there," he said. "On the interception, I was playing a deep zone. I was praying that I could see the ball coming. Then I hit my head as I fell to the ground. That made it worse."

Vaughn, who played inside linebacker at Northern Illinois, was diagnosed as having a mild concussion and was expected to be fine. Of much more concern for him Saturday night was making the team.

"I think it's a good sign for me, a great opportunity, to get that much playing time," he said. "I have to do something with that time . . . I hope I'm on the team."

Against the Rams, veteran Vernon Dean played strong safety and cornerback, both in backup roles. A starter for 4 1/2 years before losing his right cornerback job midway through last season, he will have to make this team as a utility back.

"His greatest asset is he can play both corners and both safeties," Thomas said.

Add to the equation the fact that Morrison, who is supposed to start opposite Darrell Green at cornerback, has a bruised right calf muscle and could not play Saturday. The Redskins aren't certain about his status for the Eagles game, which seems to be a common theme.