Giovanni Trapattoni and his Republic of Ireland squad headed for Portugal on Friday evening without Colin Doyle and Andy Reid.
Birmingham keeper Doyle was released from the travelling party with a knee cartilage injury after sitting out training at Gannon Park.
The 22-year-old has returned to his club for further assessment and Trapattoni will decide on Saturday whether or not to call up another goalkeeper for the training camp in the Algarve and the forthcoming friendlies against Serbia and Colombia.
His departure leaves the Italian with only 37-year-old Dean Kiely and Scunthorpe's Joe Murphy at his disposal.
Doyle's withdrawal followed that of Sunderland midfielder Reid with a hamstring problem and reduced the travelling party for the six-day trip to just 20.
The 25-year-old midfielder met up with the squad in Dublin on Wednesday but did not train this morning and the decision was made to leave him behind.
Trapattoni is already without Shay Given, Lee Carsley, Kevin Kilbane, Darron Gibson and Joey O'Brien through injury, while John O'Shea, Robbie Keane, Richard Dunne, Aiden McGeady and Darren O'Dea will not join up with their team-mates until they return to Dublin next Thursday because of club or personal commitments.
However, the manager, who put his players through their paces last night and again today, has been happy with what he has seen so far.
"The two training sessions we have had have gone very well. It is very clear that the players want to learn and advance as a group," he said.
"The tactical and technical work we did today was done very slowly so I could explain to the players exactly what it is I am looking for from them.
"Over the week in Portugal, we will do a lot more work at a greater intensity, and I am happy that we will be ready for the match against Serbia."
Ireland will face Serbia at Croke Park next Saturday evening in Trapattoni's first friendly in charge, and meet Colombia at Craven Cottage the following Thursday.
They will also play matches against Portuguese sides Portimonese and Lagos during their time in the Algarve as the manager attempts to put his mark on the squad.
Trapattoni said: "The players have the enthusiasm and the willingness to play.
"We will look at their conditioning [in the Algarve] and we have two friendly games arranged so we can check their form.
"We will know from that if they need more training or less training. This is because they have come in after the year's campaign [with their clubs].
"This is important so that we can arrive at the games against Serbia and Colombia in good shape."
