ADELAIDE midfielder Nathan van Berlo has been ruled out of Saturday night’s semi-final clash with Collingwood at the MCG, but defender Nathan Bock is a chance to return after getting through the club’s main training session.

Van Berlo, who aggravated a back injury in the round-22 win over Carlton, warmed up alongside his teammates on Wednesday morning but was forced from the track after experiencing tightness in his lower back.

Crows’ assistant coach Todd Viney said van Berlo would now turn his attention to being fit for the preliminary final, should the team overcome the Pies this week.

“Nathan’s one of the leaders of the team and he has a good finals record, so we were hoping he’d be right but you never quite know with backs,” Viney said on Wednesday.

“He did the full warm-up and a couple of other drills, but he felt his back stiffening up. We knew at that point he was probably in trouble, so we didn’t push it any further.

“The injury is not too serious. He did have something similar at the start of the year and got over it in one week, but this one just hasn’t come up. Hopefully, he can get himself right for next week.”

Bock, 26, fared better in his attempts to return after five weeks out with a fractured heel.

The All-Australian centre half-back completed Wednesday’s two-hour session and the club must now decide whether or not to bring him straight back into the team.

“Nathan feels better than last week and I thought he trained better. He didn’t look like he had the same sort of limp as he did last week,” Viney said.

“The match committee has got some decisions to make. We’ll see how Nathan pulls up tomorrow, but [we’ll have to decide] whether we play him or if he goes to Woodville-West Torrens and plays a game, or we don’t do that and we give him another full week of training".

Viney, who was part of Hawthorn’s premiership-winning coaching team last season, has experienced first-hand the risks associated with playing injured players in finals.

Last year Hawks’ defender Trent Croad went into the grand final against Geelong with an injury cloud.

Croad succumbed to a foot injury in the first half and hasn’t played a game since.

“Trent’s injury was completely different to Nathan’s", Viney said.

"It certainly does stretch you if [the gamble] doesn’t come off, but there have been numerous stories about players that have gone in injured to finals series and got through.

“It’s just a long discussion to be had and we’ll have to weigh up all the pros and cons.”

Tagger Rob Shirley (hamstring) also got through training unscathed and will be available for selection.