Jacobs jarred the medial ligament in his knee in January but has been back training fully for a number of weeks.
O’Brien impressed in his first senior opportunity in the Club’s opening NAB Challenge clash against North Melbourne in Port Lincoln on March 1, winning 14 hit-outs and eight disposals.
Crows coach Phil Walsh said the 19-year-old would lead the Club’s ruck department against the Cats in an attempt to ease Jacobs back into action.
If O’Brien continued to perform, the coach said he’d debut against North Melbourne in Round One.
“I was really happy with how Reilly performed last week, (he) did the majority of the ruck work and he’ll probably do the same again and we’ll manage Sam back in his first game,” Walsh said.
“If Reilly goes well again I’ll play him again against Port (in the Club’s final NAB Challenge game).
“(If) he puts pressure on (Josh) Jenkins, it puts pressure on how we use Jacobs – all those things.
“I’ve spoken to the players, if you play well you stay in the team and that’s how it works.”