The Italian tactician believes that although the 22-year-old possesses great ability, he must improve other areas of his game in order to assert his dominance on the pitch
The 22-year-old Wigan Athletic midfielder featured for Ireland during the 0-0 draw away to Sweden on Friday, March 22 and Trapattoni has once again included him in his starting lineup to face Austria this evening.
And despite acknowledging the player's 'quality', the former Juventus coach stressed that McCarthy needed to assert himself more on the field.
"He has great quality and he needs to improve on this," Trapattoni told reporters. "McCarthy grows as a player, and I think we need him to be more offensive. I told him that I would punch him if he doesn't stop being shy.
"He can increase and take more confidence, and in every training session I can see this. Now, we wish not to discuss his club, but I think he can play for a top team because he has good vision, he can immediately see a pass and he can shoot as well," added the 74-year-old.
McCarthy will be partnered in midfield by Stoke City midfielder Glenn Whelan, who has overcome an ankle injury and is deemed fit to face Austria.
However, doubts remain over the fitness of Whelan's club team-mate Marc Wilson, who is struggling with a groin injury and could be replaced by Reading defender Stephen Kelly in the starting line up.
The Boys in Green host Austria in a World Cup qualifier at the Aviva Stadium, tonight, Tuesday March 26.