But Fabian Hurzeler has options as he picks a side to face Liverpool.
O’Riley returned from loan at Marseille and fleetingly went on as a substitute in the defeat by Crystal Palace.
He was used as a No.10 late last season and early this term but Hurzeler sees him as an attack-minded midfielder.
The Albion head coach said: “I think in the position 6-8, so he's quite good when he is positioned in the pocket.
“He has a good left foot, he has a good understanding of the game, he has a good anticipation, he has a good finish, so he's also doing well when he attacks the opponents' box.
“I think in the pocket, that's his best position, and definitely the FA Cup can give him an opportunity to play.”
Jan Paul van Hecke and Lewis Dunk were both on the bench for the third-round win at Manchester United but Diego Coppola, who started, has since gone out on loan.
Jason Steele is expected to play in goal and Mats Wieffer is available after a toe injury.
Hurzeler said: “It has to be a good mixture between bringing in fresh legs on the pitch, but also sticking with the players we had on the pitch who did a great job against Villa.
“There will be a mixture, but our goal is to reach the next round.”