Which Cameron Mooney will show up for Geelong against St Kilda in Sunday's eagerly awaited AFL match of the season between the league's two unbeaten teams?

Will it be the inspirational, strong-marking centre-half-forward who was such a dominant figure in the Cats' drought-breaking 2007 premiership win?

Or will it be the undisciplined, bad-tempered erratic player whose poor kicking for goal cost the Cats so dearly in last year's shock grand final loss to Hawthorn and has frustrated not only Geelong fans but coach Mark Thompson throughout this season?

Mooney, who served a record four separate suspensions in the 2006 season, has been much better behaved in that regard in recent times - although he did serve a recent one-match suspension - but it is his kicking for goal that has frustrated the club this season.

It came to a head following the recent narrow win over Fremantle - when Mooney broke a tackle and ran into an open goal in the dying minutes only to nearly kick the ball out on the full - and the dual premiership player has kicked a total of 23.24 for the season.

After that game Thompson admitted that 'I really don't know what is going on with Cam's head at all'.

And television footage on Tuesday of Mooney spraying shots for goal as he underwent extra goalkicking practice would hardly have filled Cats fans with confidence ahead of Sunday's heavyweight showdown.

But Thompson is hoping the huge significance of Sunday's match - with both teams unbeaten after 13 rounds and already four games clear of the rest of the competition - will lift Mooney out of his recent wayward spell.

"Hopefully he realises the importance of the game to the club and to the season and does lift," Thompson said of Mooney on Wednesday.

"I think he is going to have to play well (if Geelong is to beat St Kilda) - everyone is going to have to lift and prepare for this game in a really professional way and Cam will be no different."

But while Mooney, who has kicked just two goals in the past three weeks despite Geelong's midfield dominance, is struggling - Thompson said the 29-year-old was still a formidable obstacle for rival teams and would be a handful for a St Kilda defence that is on course to concede the least amount of points ever in a 22-game home and away season.

"He has got that potential (to lift)," Thompson said of Mooney.

"Cameron Mooney is a really good player - we think a lot of him and he is very, very important to us."