The 32-year-old LA Galaxy striker, who is in line to win his 122nd senior international cap at the Aviva Stadium, sat out training this morning with an Achilles problem after a challenge by defender Paul McShane yesterday.
Assistant boss Marco Tardelli later insisted there was no doubt over Keane's participation on Friday evening, but Trapattoni will keep his fingers crossed until his captain, who joined up after another gruelling trans-Atlantic flight, is back on the field at the Republic's Gannon Park training base in Malahide.
Keane has admitted on more than one occasion that he has played despite not being 100 per cent fit for much of his career, and there is little chance of him crying off for such an important game.
Tardelli said: "It's no problem. For Robbie, it's just a knock. Yesterday in training, Paul McShane was very hard.
"Robbie decided to stay and rest because it is better. He needs to recover also after his trip.
"It's just a knock. I spoke with the doctor and he told me everything is okay."
Keith Andrews too was conspicuous by his absence during the open part of the session, but Tardelli revealed the Bolton midfielder had completed the earlier tactical work and had simply asked to be rested for the game with which training concluded.
He said: "For Andrews, it's just rest. He did the first part of training, the tactical part of training, and then afterwards asked us if it was possible to stay on the bench. It's no problem."
Trapattoni will hope his run of misfortune is at an end having already lost Sean St Ledger, Glenn Whelan, James McClean and Kevin Doyle for the Germany game with experienced defender Richard Dunne still fighting his way back to full fitness.
But Keane's presence in particular will be key to his plans against the Germans.
The former Tottenham frontman scored his 54th international goal from the penalty spot in Kazakhstan last month and took his season's tally for the Galaxy to 15 in Saturday's 2-1 defeat by Real Salt Lake.
Trapattoni has revealed Keane is likely to play as a lone striker against Joachim Low's men, a ploy which did not pay off against Spain at this summer's Euro 2012 finals and which was abandoned at half-time.
However, Tardelli insists that even if Keane is asked to lead the line unaccompanied, he will have support with either Simon Cox or Jon Walters in line to take up one of the wide berths in a five-man midfield.
He said: "We have strikers - we have Robbie Keane, we have Cox or we have Walters.
"I don't know who will play in the first XI, but we will certainly have two strikers on the pitch.
"Maybe one striker can play wide with just one up front, but we will have two strikers. Also [winger Aiden] McGeady can score a goal."
Trapattoni is expected to field three men in central midfield, including one whose job it will be to shackle dangerman Mesut Ozil, and Birmingham's Keith Fahey looks increasingly likely to be handed that task.
Asked what qualities the chosen man would need, Tardelli replied: "I don't know if the boss has decided on this situation, but Ozil needs a man who will press him, that's normal, because he is a good player.
"But for us, it's very important to play football against Germany because if we play well in midfield, it is possible to retain possession, and that's important."
Trapattoni last night called 21-year-old Chelsea midfielder Conor Clifford into the squad in a move which sent yet another message to Norwich playmaker Wes Hoolahan, 30, that he does not figure in the Italian's long-term plans.
Tardelli was frank when asked about the decision.
He said: "We are looking to the future and Clifford is the future."