Duff, who has hardly featured for United this season, made it through 90 minutes unscathed in the Republic's 1-1 draw with Serbia in Dublin on Saturday and his performance impressed the Italian.
But ... Duff being Duff ... pulled out of the squad to play Serbia because he had sinus trouble. Gazza may have played for Lazio wearing a mask after half his face was caved in, John Terry played on with a cracked bone in his arm, and Stuart Pearce once tried to finish a game for West Ham when he broke his leg! But Damien allegedly has a low pain barrier.
But Trapattoni has at least put the Toon player in the shop window for Kevin Keegan.
Trapattoni: "Damien Duff was extremely dangerous, especially in one-to-one situations.
"He has worked very, very hard and that is impressive because I know he was a long time out injured.
"Because he wasn't playing as much as the others during the season I felt he needed to play in Portugal and against Serbia.
"And we saw in the final moments of the game he still had the energy to go around players. That will be very important for us."