They did it as recently as Game 5 in the Eastern Conference semifinals against the Washington Capitals, when forward Mike Knuble was lost for the rest of the series with a torn hamstring. They just plugged the hole and moved on.

Simon Gagne, Joffrey Lupul, Derian Hatcher, Scottie Upshall, Mike Richards: They have all lost significant time - Gagne the rest of the season due to concussions - and the injuries never altered the team's course.

This time, though, they are really up against it.

With the Eastern Conference finals starting tonight in Pittsburgh, the Flyers have lost Kimmo Timonen, their top defenseman, with a blood clot in his left ankle.

Timonen "was hit with a shot in Game 4 against Montreal. He played in Game 5, and it continued to bother him," Flyers general manager Paul Holmgren said yesterday. "We had an MRI done on him and followed it up with a visit to a vascular surgeon today. We had a second opinion done today.

"There is a blood clot right in the front of his left foot, right about where he ties his skate. It's a quite serious thing and he needs to go on blood thinners and he's not going to be available."

Holmgren said doctors told the team that the clot would clear up in a month or 2, but that Timonen "had a glimmer of hope that he would be able to come back. But it's [Timonen's] glimmer. Right now we're treating this as if he will not be available," Holmgren said.

Timonen said last night he was examined at the Hospital of the University of Pennsylvania by Dr. Ronald Fairman, chief of vascular surgery and endovascular therapy, who said there is a chance the clot could clear up in 2 weeks, depending on how well the blood thinners work, but he did not sound optimistic.

"I asked the doctor what the risk was if I played and he said if you get hit there again, the blood clot might break up and then go down into your toes and then we would have to cut off your toes and that's not a very good scenario," Timonen said.

"It's an awful feeling. I was expecting to play [tonight] and you go into the hospital to make sure everything is all right and coming out of the hospital knowing the season is over, pretty much.

"How many times in a lifetime do you get the chance to play in the conference finals, maybe the Stanley Cup finals? It is the most disappointing moment in my life, hockeywise."

The loss is unquestionably the biggest blow to the Flyers this season, both in terms of who was hurt and when he was hurt.

Timonen, a 9-year veteran, was a 25-minute-a-game player and largely responsible for shutting down the Capitals' Alex Ovechkin in the first round and the Canadiens' Saku Koivu in the second round. In 12 playoff games, he has six assists and was a plus-5.

The Finnish defenseman, obtained from Nashville in an offseason trade, was also the top power-play quarterback. He cannot be replaced and his loss will be felt on the ice and in the locker room.

"The first thought is your teammate is not there with you and the first thought was for [Timonen]," coach John Stevens said. "He's a big part of our team and there is a deep affection for him as part of our team and a lot of respect for him on our team.

"Obviously there is disappointment that their friend is not here playing with us, but at the same time they're concerned for his well-being and, if anything, it would be motivation to play harder for him.

"He got us to this point. He's been a big reason why we're here and now it's up to us to pick him up."

The Flyers will be able to bring another defenseman into the lineup in either Jaroslav Modry or rookie Ryan Parent. But if there were one player, other than Marty Biron, whose loss could cost the Flyers the series, Timonen could be that player.

"We have had some key guys out of the lineup all year and hopefully somebody can take my role and play well," Timonen said. "I'm sure there is going to be somebody playing really well and I'm just hoping this is not a huge distraction for the team.

"This is the conference finals and hopefully those guys can focus and win a game [tonight]. I'm sure everybody is really focused and ready to go."

Stevens has been quick to make the right changes all year when faced with injuries. And he has had help from his players.

Lupul was piling up points when he went out for 12 games in February and March with a high right-ankle sprain, and as soon as he did, Scott Hartnell took his place. R.J. Umberger picked up his game through the rest of the Washington series and then early in the second round when he was asked to do more in Knuble's absence.

So now the big question: Who serves the role of Sidney Crosby spoiler and who focuses on Evgeni Malkin?

Timonen would have seen most of the action against Crosby while paired up with his young partner, Braydon Coburn. One possible combination could be Derian Hatcher with Coburn.

Hatcher has played a lot against Crosby, but Hatcher is so much bigger than the Pittsburgh forward that playing against him is likely to land Hatcher in the penalty box.

Hatcher would be better matching up against the Penguins' other star forward, Malkin, who is bigger than Crosby and doesn't go down so easily.

Whoever replaces Timonen could pair up with Lasse Kukkonen, Jason Smith or Randy Jones.

But it will not be easy to find the kind of shutdown pair they had in Timonen and Coburn.

"That word 'can't' is not in our vocabulary it seems, as of late here," Stevens said. "You can't replace [Timonen] but we will have to pick him up by committee like we've done in other ways here. Obviously on the power play it's a big loss, but Modry can come in and play second unit power play and it's going to be either Jones or Coburn stepping in on the first unit."

Stevens said he is considering the Hatcher-Coburn pairing but has not decided.

"I'm not sure yet," he said. "They've played together before and they've played well together. [Jones and Smith] have played together before. There are a lot of scenarios working through our mind. We didn't get word until today right before we left and it got confirmed when we got in here.

"We're going to have a look at a couple more things and we'll come up with something that works," he added.

The Flyers had game-planned all along to defend the Pittsburgh offense with team defense, keeping the rush to the outside and giving Biron the best possible opportunity to see shots.

They are also going to have to pressure the Penguins' forwards all over the ice, with those defensive duties falling to the lines of Jeff Carter and Mike Richards.

"This has to be about everybody," said Carter, who has stepped up his role as a defensive center through the postseason. "It's not going to be one guy or one line at time. Everybody is going to see [Crosby and Malkin]. That's just the way it is going to be with matchups and the home team having last [line] change.

"Everybody is going to have to be on the same page and make it as hard as possible, keep them to the outside. The less time they have with the puck, they less the opportunity they will have to do something with it," Carter said. *