The 30-year-old Spurs forward missed a penalty with the last kick of the first half as Trapattoni's side drew 1-1 with Slovakia in their key Euro 2012 qualifier in Zilina.
It was a vast improvement on Friday's performance, when the Republic lost 3-2 at home to Russia, but they finished the game wondering what might have been after their star player saw his 12-yard strike saved by Jan Mucha.
Keane has played only a bit-part role at White Hart Lane this season, and Trapattoni revealed he may consider leaving his captain out in the future, although he stressed he must handle the situation carefully.
The Italian said: "Missing penalties is not a problem. The problem is I know he is not 100% fit. He didn't play like he can.
"I could have given him a rest, I could have changed one or two players and in the future it's possible I could try this situation. He can improve his condition. He wanted to stay at Tottenham in August, and I agreed because I thought he would play.
"He has experience and is confident with the ball, although against Slovakia he was missing the technique a little bit. The last game he scored a goal so the goalkeeper knows where he placed the last penalty. He was tired and I could have changed him. But psychologically it's like killing him."
Source: PA
Source: PA