Adelaide is poised to break routine and give two of its players tagging roles against Collingwood in the second semi-final at the MCG on Saturday night.

In Round 19, the Crows tried to shutdown Dane Swan but let Alan Didak run free and lost the game by 21 points.

The inclusion of Robert Shirley, who'll assist go-with player Michael Doughty, suggests they've learned from their mistakes - coach Neil Craig confirming the strategy at a media conference on Friday.

"It's unlike us to do that (tag two players) but we've also got contingencies in place if we ever have to do it. We actually did it against Sydney in the second half so we have done it throughout the year but it is unusual for us to do it," Craig said.

"We think all that through and depending where people are on the ground and if we need to do it, we certainly wouldn't hesitate to do it."

"We've practiced that scenario so it doesn't dismantle us as far as our structure is concerned if we need to do that but we certainly wouldn't go in with three or four tags."

But Craig said apart from extra checking it was unlikely the Crows would tinker too much with its game plan.

"We're not going to throw out the whole way we've been playing out the window because of one game and because of what rides on the end of it, we've got to be better than that, we are not going to change everything just because the stakes are high," he said.

"What we will do as a football club is back in what has enabled us to get this far so far."

Shirley agreed the Crows may need to run with more than one player.

"Our structure suits the one tag only but because they've got so many good players in their midfield they generate the ball from there so we might have to look at it," Shirley said.

"I've played a few finals before and know it's crash and bash, there's a lot of contested footy and I'll be after it as well."

Shirley went to Swan in the team's last encounter and admits his opponent may have got the better of him in the second half.

The 29-year-old hasn't ruled out tackling Swan again but said there was a chance he may go to Didak instead.

"(Didak is a) Different type of player. Obviously he's got a bit of zip and if that's the case I'm looking forward to it," he said.

Meanwhile Craig hasn't ruled out Nathan Bock playing again this season despite being overlooked again because of injury.

"I still think he's a legitimate chance to play this year. I think he's getting better and better and better in terms of his injury, the pain is getting less," he said.