The Celtic rivals meet at Cardiff City Stadium with the visitors looking to build towards their crucial World Cup qualifiers against Sweden and Austria next month.
They will face a Wales side without star man Gareth Bale after the Tottenham winger was ruled out due to his foot injury.
But Trapattoni is under no illusions that Wales still remain a potent threat to his side's positive run of recent form, which has seen them lose just once in 2013.
Trapattoni was Italy manager when they were beaten 2-1 by Wales at a sold-out Millennium Stadium during qualifying for Euro 2004.
The atmosphere will be considerably more low-key on Wednesday night, but the Republic boss remains wary of the Welsh.
"This is no friendly," he said. "I know this country. I was here many years ago with Italy, as was their scorer that night, (Craig) Bellamy.
"We won in Italy but we lost over here and we know about this team, I have seen so many games and I know the Welsh players, they have a good mentality and they are international players.
"After this game we can reflect, and we will know from our attitude and personality whether we are ready to play against Sweden."
Trapattoni is pleased he will not have to face Bale's combination of pace, power and skill, but admits it is a shame for the home fans to miss out on seeing the Real Madrid target.
"I am a sports fan, I have 50 years in football," he said. "It is a shame for Wales and all football fans. He is the sort of player everyone loves.
"For us it is okay and I can say we are lucky he is not playing. But I understand the situation, what is important for Bale and Real Madrid whether he goes there or not."
Trapattoni confirmed Keiren Westwood will start in goal with David Forde ruled out by injury, although the Italian remains hopeful the Millwall stopper and defender Sean St Ledger may be fit to face the Swedes.
Norwich's Wes Hoolahan is also handed a start, playing in the hole behind striker Shane Long.
Gareth Bale, Aaron Ramsey and James Collins have been ruled out for Wales.
Bale has been ruled out with a foot injury, Arsenal midfielder Ramsey had been nursing an ankle injury, while West Ham centre-back Collins has been sidelined by a knee problem.
Swansea full-back Jazz Richards and Brighton midfielder Andrew Crofts have been called up as replacements.
Wales team: TBC
Rep of Ireland team v Wales: Westwood, Coleman, Clark, O'Shea, Wilson, Walters, McCarthy, Whelan, Brady, Hoolahan, Long.