Jared Payne sat out Ireland training at Carton House on Tuesday morning but will be given every possible chance to prove his fitness for the trip to Twickenham on Saturday.
Payne suffered a hamstring injury in the 10-9 defeat to France which left Ireland's hopes of a third Six Nations title on the bounce hanging by a thread.
Former Ulster team-mate Paddy Wallace told RTÉ's Against the Head programme that the centre's fitness is vital to Ireland's chances in London.
"From an Ulster point of view, because of the resources we had, his best position was full-back," said Wallace.
"He’s very, very smart, a really intelligent footballer.
"He has that sort of Kiwi way about him, it’s just in his blood.
"He kicks very well, he’s pacey, he’s great hands, a real good defender and I think he was very much missed in that Argentina game [the RWC quarter-final loss].
"We got caught out a lot in those outside channels where he has been very strong in marshalling that defensive line.
"They will be making sure he’s fit for Twickenham."
RTÉ Rugby analyst @AlanQuinlan1 calls for a little bit more imagination off ruck ball #againsttheheadhttps://t.co/RfKLUCocKU
— RTÉ Sport (@RTEsport) February 23, 2016
The versatile Payne wasn't up to this morning's session, and will work with the physio intensively before Joe Schmidt names his team on Thursday.
"Everyone trained fully today apart from Jared Payne," said forwards coach Simon Easterby.
"He trained probably 85 to 90% yesterday and ran well, but today he's going to do some work with the physios and continue that, and we'll give him until Thursday to prove his fitness."
Schmidt has called in Dave Foley, Jordi Murphy and Craig Gilroy to replace injured trio Mike McCarthy, Sean O'Brien and Dave Kearney as his resources become increasingly stretched.
Payne was the only member of the panel who didn't train on Tuesday, as Ireland head for a ground they haven't prevailed at in six years in desperate need of a morale-boosting victory.
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