Ireland centre Robbie Henshaw has a battle to prove his fitness in time to play against Romania at Wembley this Sunday.
A hamstring problem forced Joe Schmidt to leave Henshaw out of the team for their opener against Canada, which Ireland won 50-7 at the weekend.
Despite making good progress in his recovery from the injury, the 22-year-old could be given more time to ensure he is fully fit for the rest of the tournament.
"Robbie is returning to full fitness and he is very close," skills coach Richie Murphy told reporters.
"Whether Robbie will be ready for this week we are not quite sure at this moment, but we are hoping that he will.
"He trained quite a lot today and will probably have to train back with the team in our next training session, which is on Friday."
Ireland meet Italy in their third Pool D fixture on October 4.
