Travers suffered a hand injury and, after undergoing medical treatment and having an x-ray, it was decided that the AFC Bournemouth player should be released in order to let it heal.
“It is an injury that Alan Kelly [goalkeeping coach] and the Doc [Alan Byrne] has never seen…he’s got a displaced fracture of his thumb,” McCarthy told FAI TV.
“It’s really sad for us because he’s a great lad to have around the place and a good goalkeeper, but he’s got to go back and get it repaired if he wants to be ready for the start of the [Premier League] season.”
The former Shamrock Rovers goalkeeper made his Premier League debut for Bournemouth earlier this month, keeping a clean sheet against Tottenham and earning himself the man-of-the-match award.
McCarthy announced his squad for the 2020 qualifiers earlier this week with Bolton Wanderers’ Luca Connell the notable inclusion.
The Republic of Ireland are away to Denmark on June 7 before facing Gibraltar at the Aviva Stadium on June 10.