Crows' rookie facing tall task in AFL

It doesn't get much more daunting for a young AFL ruckman than going head-to-head with Fremantle giant Aaron Sandilands.

But Adelaide coach Don Pyke says he's confident Reilly O'Brien won't be overawed by the mammoth task facing him in Saturday's AFL clash at Domain Stadium.

O'Brien has been given another chance to impress after Sam Jacobs failed to recover from an ankle injury sustained against Essendon in round 19.

The 20-year-old finished his debut against Brisbane last week with 29 hitouts, 16 touches and a goal.

"We'll back Reilly in," Pyke said on Thursday.

"I thought his game last week showed that he was comfortable at the level.

"He certainly wasn't overawed by his first game."

Selected with Adelaide's first pick in the 2015 rookie draft, O'Brien was a key defender before arriving at West Lakes but is now considered Jacobs' long-term successor.

The Crows are hopeful Jacobs will only miss one more game after racking up 93 consecutive appearances before his injury.

"That ankle was a little bit worse than we initially thought," Pyke said.

"Today was the first day he ran and to be honest with you, it's going to be too tight to try and run that schedule."

Veteran midfielder Scott Thompson, who was rested last week, is one of four inclusions in the Crows' extended squad and is likely to slot in for Paul Seedsman (corked buttock).

Pyke will consider resting others depending on how they pull up ahead of clashes with Port Adelaide and West Coast.

"Obviously we come off the Fremantle game into two six-day breaks and we're always mindful of managing our players," he said.

"We'll pick our strongest available side (while) being mindful of maybe some load issues."