Midfielders Owen Garvan and Gavin Williams have been ruled out of Wednesday's friendly against Galway United at Terryland Park (KO 7.45pm). Garvan has contracted shingles, while Williams has tendinitis.
Town's head of sports science Dave Williams told the club site: "Owen has got shingles and it will lay him low for at least five or six days.
"It could be longer. We will have to see how it goes, but it may be that he misses out on the tour. He is certainly out of the Galway game.
"He has also been troubled by a spot of tendinitis lately as well and that kept him out of the Boston game, so he's not having the best of luck at the moment.
"Gavin has some tendinitis around the knee, so he needs a few days' rest just to let it settle down.
"He won't be involved in the trip to Ireland, but we hope he'll be OK for the tour."
Welsh international Williams was generally regarded as Town's top performer at York Street on Saturday, playing in a central midfield role.