Rob Kearney will have the chance to prove his fitness on Wednesday, with the Leinster full-back still in contention to face Scotland on Sunday despite "tightness" in his calf.
The 33-year-old picked up a calf issue in Ireland training on Monday, and now faces a race against time to be ready for the World Cup opener in Yokohama.
Ireland are already likely to be without Robbie Henshaw this weekend, with the powerhouse centre battling a hamstring complaint.
But Irish hopes remain high that both Kearney and winger Keith Earls, who is working through a thigh problem, can be fit in time to face the Scots.
News update. @KearneyRob had some tightening in his calf. He is being monitored by the medical team and is likely to train on Wednesday or Friday. #TeamOfUs #shouldertoshoulder pic.twitter.com/5yFpLerq29 — Irish Rugby (@IrishRugby) September 16, 2019
"Rob Kearney has a bit of tightness in his calf, and that will be managed across Tuesday," said an Irish Rugby Football Union (IRFU) spokesman.
"We hope he'll be out running on Wednesday so we will be able to update after that.
"Keith Earls ran on Monday, while Joey Carbery trained fully on Monday too."
Ireland still hope Henshaw can shake off his hamstring problem in time to feature across the tournament, but scrum coach Greg Feek said on Monday that the British and Irish Lions star is "very, very unlikely" to be fit for the Scotland clash.
Head coach Joe Schmidt has opted not to replace Henshaw, even though the likes of Will Addison remain on standby back at home.
Fears were raised on Monday that Kearney's injury issue could develop into something serious, but Ireland remain adamant that the 92-cap star still has a chance to play this weekend.
Losing Kearney, Earls and Henshaw would force Ireland to rip up their first-choice backline, but now Irish bosses are confident that will not prove the case.
Should Kearney and Earls recover then Garry Ringrose and Chris Farrell would battle it out to partner Bundee Aki in the centres.
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