Wolves welcome the Spanish side to Molineux in a last-32 first-leg (8pm), and Nuno said: "Everybody is OK.
"The exception is Ruben Vinagre. He is out, but he is really close to returning and joining the group again."
Wing-back Vinagre has been out with a hamstring issue picked up at Manchester United last month.
Visitors Espanyol, meanwhile, have not bought marquee January signing Raul de Tomas with them.
The striker has scored five goals in five games since joining them from Benfica but is injured. Marc Roca has not made the trip either.
On if those injuries will have a big bearing on things, Nuno added: "No, no. You look at the squad and see they have a lot of options. It's going to be a strong XI, for sure.
"It's a tough game. Abelardo is a good manager, I know him.
"We're going to face a very tough opponent with quality players."