When Adelaide’s stalwart ruckman Sam Jacobs went down with a knee injury in Round Two, the spotlight quickly turned to his understudy, Reilly O’Brien.

It’s hard to take positives out of a side’s primary ruckman being sidelined, but it did present an opportunity for a young Crow that had bided his time in the reserves for years.

Three seasons on from his last appearance in the senior side - which was also his second AFL game - O’Brien was primed to return to the big stage.

He wasn’t without his critics, but an impressive performance in Round Seven, just his seventh AFL game, was the perfect way to respond.

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O’Brien collected 22 disposals, 44 hit-outs and five marks in Adelaide’s gritty 17-point win over Fremantle, prompting coach Don Pyke to label it his best game yet.

“He was outstanding tonight. It’s well-known the pre-season he’s had and he’s been looking for an opportunity,” Pyke said post-game on Sunday night.

“Sam getting injured is very unfortunate for Sam, but it presents an opportunity for Reilly and he’s grabbed it and continued to blossom and get better week-in, week-out.”

Pyke felt the highly-contested nature of Sunday’s game suited O’Brien’s game style.

“It was a real physical game and he’s a ruckman that likes getting his hands dirty after the ruck contest,” Pyke said.

“He’s built a strong body and worked on his conditioning - I’m really pleased with the progress he’s made.”

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For O’Brien, this opportunity has been a long time coming.

“I feel like I’ve been ready for the last few years so it’s been good to get the chance,” O’Brien said.

“I’ve been ready to go since I played my first games in 2016, but it’s obviously helped having a bigger fitness base this year.”

It’s taken a couple of weeks to settle the nerves but O’Brien has started to feel at home in the senior side.

“I’ve been adjusting to the AFL level as I haven’t played a heap before and it’s a big jump from SANFL,” O’Brien said.

“It’s just been about getting more used to the speed of the game each week.

“I’ve continued to work on everything from my ruck craft to follow up to my aerial work, which I’ve been doing in different ways over the past few years.”

With an improved body of work behind him, the 23-year-old is confident he can challenge Sam Jacobs for first ruck when the experienced Crow makes his return in the coming weeks.

“If I can continue to improve each week, I’m sure I’ll be able to put pressure on the [spot],” O’Brien said.

As he prepares for his first Showdown, O’Brien is well aware of the task before him.

“They [Port Adelaide] have got a great ruck pairing, probably the best in the league,” O’Brien said.

“It’s going to be a challenge, they’re both good players, but I’m feeling confident and feeling good.”

“Different rucks pose different challenges, Patty’s obviously more athletic and a big jumper, while Scott’s a real strong guy so it’s about knowing your tactics at centre bounces.”

The Crows will take on the Power in Showdown 46 on Saturday night.