The 32-year old striker is in top form for both club and country, scoring twice in a friendly against Georgia on the weekend, and Trapattoni feels that he has been refreshed and reinvigorated since his MLS move.
"Robbie Keane in his career has always been an important player," said the Italian.
"In football, there are players who are clever, intelligent, and there are players who work and do their jobs, and these players become famous for their qualities.
"At 18 years old, he was already (the) Robbie Keane (we know now), in Italy and in England, and I think he can continue in this way because of his quality.
"In America, he has gained fresh enthusiasm in a new situation and he looks very, very well.
"Before the game, he was very, very sharp."
On the weekend, Keane equalled Shay Given's record of 125 caps for Ireland and took his goals tally to 56 to remain the nation's all-time leading scorer. He will become Ireland's most-capped player on Friday when he and his teammates take on the Faroe Islands in a World Cup qualifier.