Leo Cullen says he's hopeful Johnny Sexton will be cleared to return for Leinster in next week's Champions Cup opener against Racing 92 in Le Havre.
The Leinster and Ireland captain is left out of the squad for tomorrow's top of the table BKT United Rugby Championship meeting with Ulster at the RDS, with Ross Byrne starting once again for the league leaders, and Charlie Tector named among the replacements.
Sexton has been dealing with a calf injury which saw him miss Ireland's final game of the Autumn Nations Series against Australia last month.
"He's working away, trying to get back for next week, so we'll see how that goes, but he's making good progress," Cullen told RTÉ Sport.
"He didn't train with the team this week, he's just working away on his own at the moment."
While Sexton sits out tomorrow night's visit of Ulster, Cullen has been able to welcome back the majority of his frontline Ireland internationals, with Hugo Keenan, Jamison Gibson-Park, Garry Ringrose, James Ryan and Josh van der Flier all starting, with Tadhg Furlong, Andrew Porter and Celan Doris among the replacements.
James Lowe also starts on the wing, with the Ireland international set for his first appearance of the season after a calf injury.
"We've got a number of guys coming back this week, which is great," Cullen added.
"It's just freshening guys up, we've started this block of games, Glasgow last week, and Ulster is great, in terms of it being a huge game for us, first against second in the league and leading into Europe next week.
"It's two strong teams going at it tomorrow night, conditions are beautiful today but it won't be sunny tomorrow at half past seven.
"This time of year you have to be able to adapt to conditions on the day, both teams have strong forward packs and that's what they base the foundations of their game on."
While Leinster were 20-13 winners when the sides last met in September, they lost twice to Ulster last season, including a 20-10 defeat at the RDS just over a year ago.
And Cullen says they are well versed with the strengths of Dan McFarland's side.
"Ulster will test us out, a good kicking game, a strong, physical team.
"We talk a lot about Stuart McCloskey in terms of how physical he is and he delivers on a consistent basis, you saw it with Ireland in the November internationals.
"We've a number of players coming back, and Ulster are the same, who won't have played in a few weeks together. It's coming to that pivotal time of the year, it's the perfect fixture in many ways."
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