Alastair Clarkson admits his faltering reigning premiers face a major task in covering injured forward Jarryd Roughead in the run home to the finals.

Roughead, who has not missed a game since 2007, is out for the rest of the season after undergoing minor knee surgery during the week.

While the Hawks have endured countless injuries to their defenders and midfielders during what has been a tortured premiership defence - Friday night's clash will be the first time this season the Hawks have gone into a game without their successful key forward pairing of Lance Franklin and Roughead.

The pair booted 188 goals between them during the Hawks' premiership season last year and this year has combined for 109 goals despite Hawthorn having only won eight of 19 matches.

Clarkson admitted the timing of Roughead's knee injury was not good with the Hawks needing to win their last three games - starting with Friday night's MCG clash against Adelaide - if they are to avoid becoming the first reigning premier to miss the finals the following year since Adelaide in 1999.

"It's pretty difficult to cover a big brute like that in our front half," Clarkson said of Roughead.

"He has played a lot of footy for us and very consistently over a long period of time so he will be a big loss for us."

Clarkson said the Hawks will have to 'mix and match' their attack this week in an attempt to conjure a winning score - a task made more difficult by the continued unavailability of other handy forwards in Stuart Dew and Mark Williams, although that pair could return from injury next week.

The Hawks remain just a game outside the eight - and locked in a four way battle for eighth spot with Port Adelaide, Sydney and Essendon - despite having won just two of their past eight matches.

Even Clarkson is struggling to believe his team remains a realistic finals chance after such an injury-riddled and disappointing premiership defence.

"I think the AFL is giving consideration to just having a top seven because no-one seems to want that eighth spot," Clarkson said.

"We have been searching for it and I know Essendon and Port and obviously the Sydney Swans now are in contention too."

"But our guys have been preparing the same all along and we are no more motivated this week than we were last week to win games of footy."

"And I don’t imagine even if it gets to the stage where it's mathematically impossible to make the eight, we won't lose the grunt to play because we want to play out the rest of the season (strongly) whether we qualify for the finals or not."