St Kilda's bid to stay unbeaten this AFL season will be severely tested after defender Zac Dawson joined Justin Koschitzke in getting suspended for Saturday's clash against the Western Bulldogs.

Dawson paid the price for challenging his rough conduct charge at the tribunal on Tuesday night, as he was outed for two games - double what he was offered through an early plea.

He was found guilty of making rough conduct on Adelaide's Brad Symes at Etihad Stadium last Sunday night.

The Saints will also be without Koschitzke's marking strength in attack for the round-17 blockbuster at Etihad Stadium, as he accepted a one-game penalty for striking Crow Richard Douglas.

The blows mean the ladder leaders will be without two of their in-form key-position players for Saturday night's clash against the Bulldogs, who are third and represent the Saints' sternest test over the remaining six rounds.

Dawson was outed for laying a heavy bump on Symes, who had his arms in the air while standing the mark on St Kilda's Leigh Montagna in the back pocket and never saw the contact coming.

AFL legal counsel Jeff Gleeson SC argued Dawson's contact was permissible in some circumstances, but not when a player had his arms in the air, had no chance of tackling Montagna or making a smother and was oblivious to being bumped.

Dawson argued he applied a bump thinking Symes would smother Montagna's kick, but denied he used the full force of his big frame.

"I could have hit him a lot harder than that," Dawson told the jury.

Symes was left winded but recovered to play out the game, but has been put on restricted training this week.

The tribunal jury deliberated for 30 minutes before ruling against Dawson, who will also have to sit out the round 18 game against Sydney.

St Kilda football manager Greg Hutchison said the Saints were disappointed with the verdict, and did not rule out an appeal.

Dawson and Koschitzke have enjoyed their best seasons in 2009 in what has been a stand-out campaign for their club.

Dawson has been one of the recruits of the season and has played every game to this point after being picked up from Hawthorn last year and starting this season on the Saints' rookie list.

Koschitzke has booted 36 goals from 15 games - his best tally for a season since he made his debut in 2001.

Koschitzke's absence at least allows him to nurse the cut hand he suffered against Adelaide.

Bulldogs coach Rodney Eade, speaking before Dawson was suspended, said the suspensions would have little effect on the game.

"Teams have good players out. When we played Geelong we had (Ryan) Hargrave and (Robert) Murphy not play," he said.

"Teams cope with players out, so you just move on."

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