The Dubliner has returned to training with his club after two operations on a groin problem amid speculation that he could be shown the door by Villa manager Paul Lambert in January.
"Richard has had a long injury and it's a bit difficult to get back," said Trapattoni.
"We have to continue with the new, with (Sean) St Ledger and (Darren) O'Dea and (Ciaran) Clark. We need to have this evolution."
St Ledger is also out through injury this week, while Toronto-based O'Dea is a slight doubt. That could open the door for Clark, who has taken Dunne's place at club level, to start an Ireland game in his natural role.