But Republic boss Trapattoni said today the 27-year-old was "not 100% fit", confirming Doyle would play no part against the Croats and instead return to his club.

Several other players had already withdrawn from the squad before Doyle, with Jon Walters, Marc Wilson, James McCarthy, Seamus Coleman and Damien Delaney among the most recent, and Trapattoni believes footballers are not being allowed enough time to recover their strength over the summer months.

"I had fears before the end of last season," the Italian said.

"I didn't want to bring myself bad luck, but I thought they were starting very early with the season. Footballers are not iron men - they need to recover.

"It is not just this friendly game that makes a difference - there are a lot of other matches that the players have had to play in pre-season.

"Now every game is very difficult. Famous teams go to play in tournaments where they can earn a lot of money.

"The teams just play, play, play. The break is very short - it is not enough."

Doyle was sidelined for most of Wolves' ultimately successful battle to avoid relegation from the Barclays Premier League at the end of last season after picking up the injury in Ireland's Euro 2012 qualifier against Macedonia in Dublin.

Trapattoni stressed the decision to send the player back to the midlands had been taken as a precaution, but was uncertain of Doyle's chances of being available for the Republic's potentially crucial qualifying double-header against Slovakia and Russia next month.

Asked if he thought Doyle might be fit in time, Trapattoni said: "We hope so. It is a difficult situation, because he will now be with his club.

"Yesterday I said 'I have to check Kevin' because the injury he had was very bad - I needed to check him psychologically.

"He was in a little bit of pain and I said 'it's better you stay (with Wolves) because of (the games in) September'."

Despite the setbacks, Trapattoni is determined to send his side into tomorrow's match in a positive frame of mind.

Since the end of May, Ireland have won four games in a row without conceding a goal - including a second qualifying victory over Macedonia and an impressive 2-0 friendly triumph against Italy with a much-changed team - and the manager is keen to keep the momentum going.

"I don't like to cry about missing this or that," Trapattoni said.

"No - we are a team, and we have shown that. We are missing seven or eight names, but the team has not changed too much in terms of the system. In the last months we have changed the players, but not the gameplan.

"Croatia are a strong team with many players who play in England.

"It is a good test for us and it is important that we don't forget what we have done, how we achieved these results - with attitude, order, mentality, performance and overall, belief in our project, in our system."

Ciaran Clark has come in to replace Delaney and Trapattoni has also called up Chelsea youngster Conor Clifford to provide cover in midfield.

Clifford, 19, will join up with the seniors after playing for the Under-21s against Austria in Sligo this evening.

Striker Shane Long, who was yesterday reported to be in talks with West Brom about a move from Reading, trained with the group at Malahide this morning and will start tomorrow night alongside captain Robbie Keane.

Team: Shay Given; Stephen Kelly, Richard Dunne, Sean St Ledger, Stephen Ward; Damien Duff, Glenn Whelan, Darron Gibson, Stephen Hunt; Shane Long, Robbie Keane.