Ulster will give Stephen Ferris every chance to prove his fitness ahead of Sunday's Heineken Cup tie with Munster.
Coach Brian McLaughlin hinted Ulster may include the injured flanker in the starting XV when the team is named at noon on Friday.
McLaughlin said it is "impossible" to predict how Ferris' ankle injury will respond to treatment during the week.
"He is comfortable. We will reassess the situation daily and we will leave a decision until as late as possible."
McLaughlin said he has every faith in the Ulster medical team to get Ferris back out on the field after he sustained lateral ligament damage to his ankle during the league win over Aironi last Friday night.
Ferris missed last year's Heineken Cup quarter-final defeat to Northampton Saints with a serious knee injury and is determined not to miss out on playing in the knockout stages for the second year in a row.
Ulster are likely to name him in the starting team, which will give him another 48 hours to recover before the last eight show-down with Munster at Thomond Park on Sunday [13:45 BST].
"We'll sit and have a chat and see how much of the captain's practice he's able to do, if anything," said McLaughlin.
"It is a race against time. He wants to play, we want him to play, and we want to give him as much time as possible.
"He missed out last year. He got a knee injury in Aironi, which nearly robbed him of his World Cup as well.
"So from that point of view, we are obviously keen as a team for Stevie not to miss out this time and we'll be doing everything in our power to make sure that he is fit to go.
"But like I said, it is a race against time. To put a percentage on it, at this stage, is impossible."
Paul O'Connell has been passed fit to play in the quarter-final.
Ulster captain Johann Muller has compared O'Connell's influence on the Munster team as similar to the impact Stephen Ferris has with Ulster.
"I have played a couple of games against Paul and he is one of the best locks I have ever played against, if not the best," said Muller.
"He is an outstanding rugby player and an outstanding leader and that is what he brings to the team. He lifts everybody around him.
"He is probably as important as Stephen is to us. He is massive. He is a great player and it is difficult just to get another player to fit into their shoes.
"They are both world-class players."