United were beaten 2-1 by Championship side Bristol City in the quarter-finals of the EFL Cup last month.
Paul Pogba and Zlatan Ibrahimovic both started that match at Ashton Gate but could not prevent the visitors from exiting the competition after Korey Smith struck a dramatic stoppage-time winner for Lee Johnson's men.
Mourinho is wary of suffering a similar fate against another of the teams chasing promotion from the second tier.
"The draw was not nice to us because we are going to play against a Premier League team," Mourinho told a news conference on Thursday ahead of the third-round tie at Old Trafford.
"If you look to the [Derby] players they are not Championship players, they are Premier League players. I think I played against the majority of them in the Premier League.
"So when you go to [Scott] Carson, Curtis Davies, [Joe] Ledley, [Matej] Vydra, [Tom] Huddlestone, I played against all of them."
Mourinho is adamant he picked a strong starting XI for the trip to Bristol and plans to do so again on Friday.
He said: "I'm going to do the same against Derby County; I'm going to play with a good team, then the result is out of your control but to go with a strong team with first-team players, first-choice players, for sure."
The Portuguese boss confirmed Romero would take over from first-choice shot-stopper David de Gea between the posts.
"I'm going to play this match like a Premier League match and I'm going to play Romero because Romero is a top, top goalkeeper and he deserves to play and David deserves a rest," he said.
"Romero is going to be Argentina's goalkeeper in the World Cup in a few months, so for all that Romero means to us Romero plays and apart from that I am going to play with a team I consider a very strong team."
According to Mourinho, Romelu Lukaku is available after being cleared of concussion, while Marouane Fellaini has also recovered from a knee injury.
"Romelu is OK, Fellaini is back," the manager said.
"And Michael Carrick is back training, not in competition. [Antonio] Valencia will be back to the team next week, so not playing tomorrow, back with the team next week. The situation is improving for us."