"He will come maybe tonight or tomorrow," added Trapattoni on Saturday morning.
Trapattoni's side play a practice match against Portimonese on Sunday before facing Lagos on Monday and the Republic boss intends to use all 20 squad members in the matches.
Serbia are the opposition in Dublin on 24 May followed by Colombia at Craven Cottage on 29 May.
West Bromwich Albion keeper Dean Kiely is back in the Republic set-up after a five-year absence.
There are seven uncapped players in the panel - Owen Garvan, Wes Hoolahan, Sean Scannell, Kevin Foley, Darren O'Dea, Damien Delaney and Glenn Whelan.
Robbie Keane and Richard Dunne will meet up with the squad after the Portugal camp, which starts on Saturday.
The Tottenham striker and the Manchester City defender are among five men who will join up with the rest of the 28-man squad in Dublin on their return because of club or personal commitments.
Champions League finalist John O'Shea, and Celtic duo Aiden McGeady and O'Dea are also missing the trip to Portugal, while Cardiff midfielder Stephen MacPhail will arrive after Saturday's FA Cup final.
Republic of Ireland squad - goalkeepers: Dean Kiely (West Brom), Joe Murphy (Scunthorpe), K Westwood (Carlisle Utd).
Defenders: Alex Bruce (Ipswich), Damien Delaney (QPR), Richard Dunne (Manchester City), Kevin Foley (Wolves), Stephen Kelly (Birmingham), Paul McShane (Sunderland), Darren O'Dea (Celtic), John O'Shea (Man Utd).
Midfielders: Damien Duff (Newcastle), Owen Garvan (Ipswich), Wes Hoolahan (Blackpool), Stephen Hunt (Reading), Aiden McGeady (Celtic), Stephen MacPhail (Cardiff), Liam Miller (Sunderland), Darren Potter (Wolves), Andy Reid (Sunderland), Martin Rowlands (QPR), Sean Scannell (Crystal Palace), Glenn Whelan (Stoke).
Strikers: Kevin Doyle (Reading), Robbie Keane (Tottenham), Andy Keogh (Wolves), Shane Long (Reading), Daryl Murphy (Sunderland).
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