Ireland hooker Rónan Kelleher has been ruled out of next month's autumn internationals due to a hamstring injury.
Kelleher, who missed Ireland’s series win in New Zealand with a shoulder problem, faces up to eight weeks out with his latest injury.
As well as being absent for Ireland’s November Tests against South Africa, Fiji and Australia, Kelleher faces a race to be fit for Leinster’s Heineken Champions Cup opener against Racing 92 on 10 December.
Kelleher’s Leinster team-mates Harry Byrne and Will Connors also face spells on the sidelines.
Byrne could miss eight weeks with a hamstring injury while Connors faces 12 weeks out after undergoing a procedure on the bicep injury he suffered against the Cell C Sharks.
Connors was sidelined for seven months with a knee injury earlier this year. He made his return in the season-opening win over Zebre Parma only to suffer another setback in his fourth appearance of the campaign.
"Will has been particularly unlucky," said Leinster senior coach Stuart Lancaster. "He takes one step forward and then unfortunately gets an injury and has to take one step back.
"The good thing about Will is he has an incredibly positive mindset and the form he showed at the start of the season means that once he gets over this bicep injury he'll be back soon enough.
"He’s got the Christmas period and five or six months in the second half of the season to aim for, including the Six Nations and hopefully a World Cup."
Luke McGrath, Rhys Ruddock and Ryan Baird continue to follow graduated return-to-play protocols, having missed the win away to Connacht, and could return for Saturday’s Aviva Stadium derby against Munster, live on RTÉ2 and RTÉ Player.
Jack Conan (eye), James Ryan (knee) and Josh van der Flier (ankle) all picked up knocks in the 10-0 victory in Galway and require further assessment this week.
Dave Kearney, who suffered an abductor injury against Ulster, is expected to return to full training this week while Ireland full-back Hugo Kennan is also stepping up his rehab from abdominal and knee injuries.
Watch Leinster v Munster in the United Rugby Championship on Saturday from 4.30pm on RTÉ2 and RTÉ Player, listen to live commentary on RTÉ Radio 1's Saturday Sport and follow a live blog on RTÉ.ie/sport and RTÉ News app
