On Monday, the Dolphins made the anticipated decision to place nose tackle Jason Ferguson on the injured reserve list, causing a premature conclusion to the season for another team captain and key contributor.

Although it's tough to argue one injury as more significant than another -- especially when other players have included quarterback Chad Pennington and running back Ronnie Brown -- the task of replacing Ferguson is surely among Miami's biggest challenges yet.

``It's tough,'' defensive end Randy Starks said. ``Without your nose [tackle], you don't have a defense. He pretty much kept the defense together.''

Coach Tony Sparano did not yet know Monday afternoon whether Ferguson would require surgery to repair an injured quadriceps (not a knee, as initially diagnosed), but he still knew enough to realize this: The Dolphins must find a way to move on without him.

``Nobody is going to feel sorry for you, and if you start feeling sorry for yourself, you're going to be on the wrong end of a real good butt-kicking,'' Sparano said. ``We're not going to do that.''

Nonetheless, Ferguson's absence will leave a gaping hole in Miami's front line for two reasons: First, the veteran has seven more years of experience than the Dolphins' next most-experienced lineman. His leadership is crucial.

Second, the nose tackle in a 3-4 defense is arguably the most difficult defensive position to fill, mostly because it requires a rare combination of a massive frame, quick feet and above-average intelligence.

Consider this quote from Tony McDaniel, a defensive end who now will be asked to move inside to spend some time at the nose: ``I'm tall and lanky, so I'm more fit for a defensive end. I don't really look like a nose tackle.''

Only when comparing himself to a nose tackle could a 305-pound man describe himself as ``lanky.'' Starting to understand the challenge facing Miami?

``Nobody can fill his shoes, but I think we have enough guys in the room who can help contribute together,'' Starks said.

So yes, Ferguson will be tough to replace. But no, the task isn't impossible. To accomplish the task, the Dolphins will first hold out hope that backup Paul Soliai, who is having his best season as a pro, can return this week from an ankle injury.

Sparano, without delivering any full-blown updates on any other injured players (it will not be until Wednesday to know more about center Jake Grove's ankle injury as well), at least sounded optimistic when mentioning Soliai's possible impact.

``I would hope that Paul Soliai is ready to go, and he would have to step in there and play,'' Sparano said. ``Now the last time that happened, [Soliai] played pretty good. I would hope that's where we are.''

NEED FOR ROTATION

``We'll see as the week goes on, but just like Ferguson and Soliai, one person can't play the whole time,'' Sparano added. ``You need to have some people moving in and out.''

Those players behind Soliai -- assuming Soliai is able to play against the Bills on Sunday -- will be Starks and McDaniel, two big-bodied defensive ends who at least play with an aggressive style that will help wear down opposing centers to put Miami's linebackers in the best position to stop the run.

There's also a chance, when Ferguson's roster spot opens up after he is formally placed on IR, that Miami could fill that vacancy by signing Ryan Baker from the practice squad. Baker is a developmental player who showed nice versatility and progress along the defensive line during training camp.

Those decisions will be important to the short term. But the long-term stability of the nose tackle position also will require conversations within the Dolphins' front office. Ferguson, 34, is not under contract with the Dolphins beyond this season. During training camp, he made it pretty clear he would only want to continue his NFL career if he were playing in Miami under this regime.

Whether the Dolphins decide to bring Ferguson back could be dictated by the success of his rehabilitation from the quadriceps injury he suffered in Thursday's game. Given the difficulties in finding solid nose tackles in a 3-4, Soliai's performance in the next six weeks also could help dictate that decision.

`MENTAL TOUGHNESS'

In the meantime, Miami must find a way to quickly rebound from another tough blow to a roster that is suddenly decimated by injuries. No matter the position, and no matter the player, Sparano said he knows there's only one way for the Dolphins to respond.

``We have six games left here to try and get ourselves in position to get into this tournament down the road,'' Sparano said. ``There is going to be a lot of mental toughness required. Now, there has been a lot of mental toughness required to get us back to where we are right now, so I have confidence this team will carry that out.''