Washington Redskins quarterback Mark Rypien will undergo an arthroscopic examination of his left knee this morning to determine how much, if any, serious damage he sustained during Sunday's 19-15 victory over the Dallas Cowboys.

Rypien appears headed for injured reserve, which would sideline him a minimum of four weeks. But the Redskins said no decision will be made until after today's surgical procedure that amounts to a thorough exam of the area.

Rypien last night remained hopeful he could be back on the field in two weeks, saying, "I'm hoping for the best."

Meanwhile the Redskins named Stan Humphries to make his first career start this Sunday at Phoenix, and signed veteran Gary Hogeboom to back him up for at least this week. Coach Joe Gibbs refused to say the top job would necessarily be Rypien's when he returns.

"It'll depend on what happens between now and then," Gibbs said. "We'll have to see how Stan's doing and how the team is doing."

Gibbs clearly threw the door open for Humphries, 25, to win the job, saying: "Stan knows the future is right out there on Sunday. This is an opportunity he has worked for. He's worked three years and he's got to seize it. . . . He can step up right now. It's going to be exciting for him and exciting for us."

Jeff Rutledge, the former New York Giants backup who is on Redskins' injured reserve, can practice after this week's game and Gibbs said Hogeboom's future with the Redskins "will be tied to Rip's health."

General Manager Charley Casserly contacted the former Cowboy, Colt and Cardinal at halftime of Sunday's game, just moments after Rypien was injured. He said Hogeboom was a clear No. 1 choice since, having been in training camp with ex-Redskins assistant Joe Bugel's Cardinals, "he knows our system," Gibbs said. "He had a full camp in a system exactly like ours."

Casserly and Gibbs said Doug Williams, released by the Redskins last winter, was never a consideration.

First, they said they considered only quarterbacks who'd been in training camps this year.

Second, Gibbs said the reasons Williams was released remain valid. Gibbs revealed publicly for the first time that he told Williams in a face-to-face meeting in February that he was being released because of concern for his health.

He said that Williams asked Gibbs not to publicly announce the reason for fear it would hurt his chances of catching on with another team. But after Williams wrote a book, "Quarterblack," criticizing Gibbs for releasing him, Gibbs apparently believed their confidence had been violated and felt compelled to tell his side of the story.

"I think this is important for everybody to know because I'm sure there are questions in the community and other places," Gibbs said. "With Doug, it was the original reasons why we released him. At that time, I couldn't elaborate a lot on those because I'd been asked not to by him. My overriding concern was his health. He'd had that knee {problem} a long time and then to have major surgery on your back, I felt like it was getting to the point that he was putting himself at risk. We talked originally and he asked me not to say anything about it. And I didn't. . . . Secondly, there was the fact he hadn't been in camp this year. I thought that would be next to impossible for a guy to come in that had been totally out of football, to ask him to step in and play this week."

Williams was unavailable to comment.

As for Rypien, today's exam by team physician Charles Jackson should answer several questions. It appears he has some damage to the posterior cruciate ligament, but it could be so minor that no repair work will be needed.

Jackson will also try to find out why Rypien has been unable to straighten the leg. One reason could be that a piece of cartilage or meniscus tissue broke off and lodged in a way that prevents him from doing so. Jackson warned that the answer could be simpler, a matter of inflammation and swelling. One option was to wait a week and see how much of that had gone away. But he also said: "We could have waited a week and found that he still needed to have this work done. He'd be a week behind by then."

Jackson said if no damage is found Rypien could be back practicing in about two weeks. But team officials warned that such a prognosis was overly optimistic.

If Rypien isn't placed on injured reserve, he'd still be part of the 47-man roster on Sunday. That would mean a player would have to be cut to make room for Hogeboom, who definitely will be activated.

Rypien tried to take the news in stride. Kicker Chip Lohmiller drove him to the taping of his television show, then to Redskin Park for his appointment with Jackson. Rypien and Humphries spoke privately after an afternoon TV interview and Humphries said he told him essentially: Get well soon.

"I'll admit this isn't one of my better days," Rypien said. "I didn't think it would be this stiff today, but the doctor warned me the second day would be worse than the first. I'd like to think it's not a four-week deal."

He shrugged: "I'm lucky the guy {Dean Hamel, rolled into him by guard Mark Schlereth} hit me straight on. If he'd rolled into the side of my leg, it would have been totally blown out. Right now I'm going to be a cheerleader."

Humphries said he realized the opportunity that lay in front of him. He was five of 13 for 58 yards after replacing Rypien, although at least four passes were dropped.

"I've got to do better," he said. "The way I look at it is that if some of those passes had been thrown better they wouldn't have been dropped. Right now we've just got to come out and work together. I think I can do some things to help this team and we'll go from here."

Humphries has a chance to rescue an offense that has been in a three-week slump and scored nary a touchdown against the young Cowboys. Gibbs said he had no explanation for the eight dropped passes, 11 penalties and generally poor execution in several areas Sunday.

"Everything just sort of combined to keep us from getting anything done," he said. "We had the ball inside the 10-yard line several times and we stopped ourselves with a number of penalties and drops. We were very inconsistent. We've got exceptional receivers and for them to drop some passes, I don't see any logic for it."

Another problem has been a running game that is averaging only 94.7 yards per game. He said his offensive line "played darn good" in pass protection, but "the run-blocking is a place we're down. It might be that we're not getting enough attempts running the ball, and we're going to try to balance that up."

Gibbs went looking for a spark last season in Week 9 when he inserted Williams into the starting lineup against the Cowboys -- who won, 13-3 -- and he seems to hope Humphries can provide a spark that catches.

"I'm curious to let him get out there and play," Gibbs said. "When we've given him an opportunity, he has made some of the best plays I've ever seen. . . . He's got a real good arm and can move around a little bit back there. Quarterback is unusual and it really comes down to taking the team and moving it down the field. This is Stan's chance."