The Wigan Athletic midfielder is carrying a slight groin strain but the Italian tactician is hopeful that he will be available to play against the world and European champions
The 22-year-old Wigan Athletic midfielder is suspended for Ireland's World Cup qualifier against the Faroe Islands on Friday, June 7 and has been allowed to leave the squad, but Trapattoni believes that it would ultimately be beneficial for the player to play against the reigning world and European champions.
"I think he is 90 per cent certain to come," Trapattoni told reporters. "He has two or three situations to sort out but it is important for him to travel and he would benefit from even 30 minutes against the Spanish; it would help the development of his personality."
The former Juventus boss said that McCarthy has not ruled himself out of the friendly, which will be played at Yankee Stadium in New York on Tuesday, June 11. However, the Italian tactician stressed that the Irish players must show supporters respect and take the fixture seriously.
"He has never said that he won't go," added Trapattoni, "And I know I would never have turned down such an opportunity but he does have a little bit of pain in the groin.
"If he has pain it would be impossible for him to play but I hope he can; Spain have agreed to this game and the Irish supporters in New York deserve respect, our players must understand this.
"It's only three days and for me it's incredible that anyone would say that they need to rest. In 1982, when Juventus won the championship, Marco [Tardelli] and seven other players went to the World Cup and we then went on to Washington where we met (then vice-president George) Bush and played a friendly."
"The FAI have made a commitment, the Irish people have paid for tickets to come and see us so we must go," concluded Trapattoni.
Meanwhile Hull City midfielder Stephen Quinn has revealed that it was a "great feeling" to have picked up his first senior international cap.
The 27-year-old was handed his senior international debut when he replaced Wes Hoolahan against Georgia as a 75th minute substitute. Quinn, who picked up nine under-21 caps for the Boys in Green, scoring one goal, explained that it was an "honour" to play alongside Robbie Keane and Richard Dunne
"It was a bit of a monkey on my back, to be honest," he told the Irish Examiner. "I've been waiting all my life for this first cap, so to get it is a great feeling. To play with such legends as Robbie Keane and Richard Dunne before they end their careers was a real honour."