O’Carroll, 24, signed from Wigan in the close season and was a stand-out performer in the pre-season friendlies against Bradford and Hull KR, before a back injury ruled him out of the early stages of Hull’s season.
But he has returned to first team training this week, and is in contention for selection for Sunday’s game against Wakefield.
O’Carroll told the club’s official website: “After my injuries over the past few years, to miss the first few rounds of the new season was really disappointing and frustrating for me.
“I had a really good off season with no injuries, but I was just a little unlucky by pulling my back in the gym during training.
“Being a bit eager to get back into the team, I then just twinged it again but I’ve taken my time with it now and I’m looking forward to the Wakefield game if Peter selects me.”