Ireland wing Andrew Trimble will have a further scan on the ankle injury he picked up in Saturday's win over Wales after a first look was inconclusive.
Trimble had to be replaced before half-time and Ireland kicking coach Richie Murphy said the injury "isn't simple".
"The scan was a little bit inconclusive so he's going back in tomorrow for another scan," said Murphy.
Ulster hooker Rob Herring and Leinster centre Noel Reid have been cut from Ireland's World Cup training squad.
At this stage, there is no major concern around Trimble's fitness but he is unlikely to be considered for Saturday's second World Cup warm-up match against Scotland in Dublin.
The Millennium Stadium contest was Trimble's first game since last October after toe surgery and he looked in impressive form before having to be replaced.
|Ireland's remaining World Cup warm-up games|
|Scotland (home)||Saturday, 15 August|
|Wales (home)||Saturday, 29 August|
|England (away)||Saturday, 5 September|
Trimble, 30, was Ireland's player of the year in 2014 but missed all of this year Six Nations because of his injury.
The departure of Herring and Reid reduces Ireland's training group to 42 players, with the final 31-man squad set to be finalised on 31 August.
The two 25-year-olds have both won one cap - featuring as replacements in the same match against Argentina last June.
Barring injury, Rory Best, Sean Cronin and Richardt Strauss are certain to be Ireland's hookers at the tournament.
But Reid's omission does little to clarify the midfield options, with seven potential centres remaining in the training camp.
Robbie Henshaw and Jared Payne were Ireland's centres for the entire Six Nations, while Keith Earls, Gordon D'Arcy and Darren Cave also provide midfield options.
Luke Fitzgerald has operated at centre for Ireland but has played the majority of his recent rugby at wing, as has another utility back Fergus McFadden.
Ireland coach Joe Schmidt is expected to reduce his training group further this week before finalising his squad at the end of the month.
Munster flanker Tommy O'Donnell has already been ruled out of World Cup after dislocating a hip during Saturday's Cardiff game.
Fitzgerald and prop Marty Moore are both fit for Saturday's game against Scotland after recovering from shoulder injuries.
Cian Healy is still unavailable because of a neck injury, though Murphy said on Tuesday the prop is "progressing well".
"He's not doing full contact but he's doing more or less the whole session yesterday and today," added Murphy.
Ireland start their World Cup campaign against Canada in Cardiff on 19 September.