Whitnall was ruled out of the club'sSaturday clash with Fremantle last Friday after finally succumbing to a problemthat had plagued him for nearly two months.
Pagan said the captain "justneeded a break" from the rigours of playing, and forecast a four-week layoff asthe worst-case scenario.
"Lance's knee is still a bit sore, he hasn'tbeen out on the track yet, and he's working very hard cross-training," he saidon Wednesday.
"It's very hard to play league football. Lance wasn't ableto train properly for six weeks and we just thought it was best that he got hisknee right and then take it from there.
"He'll probably miss two or threeor four weeks, and I can't be any more definitive than that.
"He's got adegenerative knee injury. How long do they take to heal? They never become 100per cent again. We've got to manage it, and it's as simple asthat."
After admitting Whitnall's knee is not expected to return to fullstrength, Pagan said he isn't convinced the 27-year-old's best football isbehind him.
"There are plenty of people in AFL football with knees likeLance, and there would be a lot with worse," he said.
"You just have yourmoments where they flare up, and once they settle again, you can goon.
"I can't see any reason why Lance can't get his knee rightagain.
"He's a very smart player, and it wouldn't surprise me if he comesback bigger and better."
A four-man group selected by the match committeethat consists of Jarrad Waite, Brendan Fevola, Kade Simpson and Heath Scotlandwill rotate the skippering duties in Whitnall's absence, with the leadershipgroup voting for Waite to kick off proceedings this weekend.
In anotherblow for the Blues, promising Irish rookie Aisake O'hAilpin may miss the rest ofthe season if the club's fitness staff decides his on-going groin complaintneeds a tendon-release operation.
"The club is going through the processnow of determining whether he needs surgery or not," Pagan said.
"I thinkthe decision will be made by the medical staff perhaps today. It would be thetendon-release surgery that's done up in Sydney, but we haven't been briefed bythe medical staff yet and we'll find out a little more about ittoday."
Pagan, who said the younger O'hAilpin brother is a part of theBlues' future, is remaining positive and believes there is a chance his seasonis not yet completely over.
"It's very hard to say. Who knows with thosegroin injuries? He's missed three weeks with it now, he's played under duress,"he said.
"I wouldn't say it's over. It's such a fine line; you can restthem for three months and you start training again and they're better off. It'ssomething the medical people will determine as soon as they get the results ofall the scans and specialist reports.
"They'll make the right decision byAisake, and we think he's a player of the future, so we've just got to wait andsee what happens."
After a disappointing loss to Hawthorn in the firstweek of the split round, Pagan said his players were looking to atone for the100-point defeat and had improved their mindset.
"We were going so welland the whole joint looked terrific, and you say to yourself, 'Why do thesethings happen?'," he said.
"I suppose we look at last weekend and it wasprobably an attitude weekend. There were so many sides that looked like theywere ready for good games, and did completely the opposite.
"We wereprobably as bad, if not the worst, of everybody. What changes in the space of aweek? I don't think your chest gets any bigger, or your arms or biceps get anybigger, or you kick the ball 10 feet further.
"They only thing thatchanges is your mind, and the only thing I can come up with is we got in frontof ourselves against a very good side, and I think we went into panic mode andwe were dictated how we were allowed to play the game.
"We've spokenabout it like we do with any loss, and we'll learn a hell of a lot from it. I'msure if our guys had the opportunity to play it again we wouldn't get the sameresult. I'm not saying we'd win, but you wouldn't get the sameresult."
Pagan also said Eddie Betts, who has not played senior footballsince round eight witha hamstring injury, is available for selection this week,while Josh Kennedy and Adam Hartlett are pushing for a position after promisingperformances in the VFL.
