Fitness race for Ireland's Rob Kearney
Rob Kearney faces a race against time to be fit for Ireland's RBS 6 Nations clash with Italy in Dublin on Saturday.
The British and Irish Lions full-back has picked up a hamstring strain and must prove his fitness on Thursday morning.
Fit-again Jared Payne will be waiting in the wings to slot in at 15, in a move that would allow boss Joe Schmidt to pair Stuart McCloskey and Robbie Henshaw in the centres again.
"Rob Kearney had a slight hamstring issue so he sat out training," said Ireland scrum coach Greg Feek.
"Tommy O'Donnell trained fully today so he's good. Eoin Reddan had a calf issue so he sat out training as well.
"We'll wait until Thursday to assess Kearney and Reddan."
Kearney missed Ireland's 16-16 draw with Wales with a hamstring issue before returning just in time for the 10-9 defeat to France in Paris.
The 29-year-old is against the clock in a fitness battle for the second time in the tournament then, with head coach Schmidt likely to hand one of his most trusted lieutenants as much leeway as possible.
Simon Zebo could also deputise at full-back should Schmidt opt to restore his first-choice centre pairing of Henshaw and Payne.
Ulster powerhouse McCloskey impressed despite Ireland's 21-10 defeat to England on his Test debut at Twickenham in the last Six Nations outing however.
Head coach Schmidt's men are desperate for their first win at the fourth time of asking this weekend, to boost a disappointing tournament that has already seen Ireland concede the title they have held for the last two years.
Ulster's New Zealand-born three-quarter Payne admitted he will be happy to feature at either 13 or 15, having recovered from the hamstring problem that kept him out of action at Twickenham.
"I've always played wherever," said Payne, who switches comfortably between full-back and outside centre at Ulster.
"I'd played a lot of 13 in New Zealand and there were a few injuries at Ulster when I arrived so I was happy to slot in at full-back.
"But playing well for UIster is different from turning it on for a Test match.
"I think Joe would be silly not to look at the centre combination of Stuart McCloskey and Robbie Henshaw again at some point.
"They were pretty impressive against England, so I'm sure there'll be another chance to see them at some stage.
"Italy are going to be tough, they have some very good outside backs.
"So from full-back, wing or 13 they are all going to be pretty dangerous.
"So you have to be on top of your game to handle that and they will really test you.
"They've got some dangerous runners out there.
"I don't know if this is a game where you can shine at 15: you'd have to be pretty tight on your field positioning and defensive work to keep them quiet."
Payne admitted whoever starts at outside centre will face a tough battle to contain Italy's Exeter Chiefs centre Michele Campagnaro.
"Whoever marshals Campagnaro will have their work cut out and it will be tough," said Payne.
"He's probably been the form outside centre throughout the Six Nations I think.
"He's very quick and quite surprisingly strong, so whoever's got the job of looking after him will have a tough day.
"That would be nice to do that, but if you're at the back you run around a bit too, so you just do whatever you do."