John O'Shea and Aiden McGeady will go straight into the Republic of Ireland team for Thursday night's friendly clash with Colombia.
Manchester United defender O'Shea, 27, and his 22-year-old Celtic compatriot will start the game at Craven Cottage after joining up late with the rest of the party.
O'Shea and McGeady missed last week's training camp in Portugal because of United's involvement in last Wednesday night's Champions League final and the Bhoys' Scottish Premier League title triumph 24 hours later.
However, they arrived in Dublin over the weekend and have proved themselves ready to take their place in Trapattoni's plans.
O'Shea will line up at right-back in place of Stephen Kelly with Richard Dunne once against partnering Paul McShane in the middle, while McGeady will replace the injured Stephen Hunt, who was sent home last night with a hamstring injury, in midfield.
Speaking after training at Malahide this evening, Trapattoni said: "Stephen Hunt had an injury from five weeks ago and during the match the other day, he felt it.
"I let him go home because it was impossible for him to play in the match. There was no point keeping him here if he couldn't play.
"I spoke to McGeady yesterday about whether he can play or not, and he showed today he is ready, as did John O'Shea."
They are likely to be the only changes to the side that drew 1-1 with Serbia at Croke Park on Saturday evening as Trapattoni begins his preparations in earnest for the World Cup qualifying campaign, which kicks off in September.