Mourinho said goalkeeper David de Gea was the only player rested for the fifth round tie at the weekend and he was forced to add youngsters Ethan Hamilton and Angel Gomes to make up the numbers on the bench in the 2-0 win at the John Smith's Stadium.
"I didn't rest one single player, so we had every player available here (against Huddersfield)," the Portuguese manager told reporters after the match.
"I brought two kids (Hamilton and Gomes) that played 90 minutes yesterday (on Friday for the Under-23s) because I don't have another player.
"Can we recover some of them for Wednesday? I believe so. "Rashford, Herrera, Valencia, I think they have a chance. Paul (Pogba), I don't know."
Mourinho said Jones and Rojo were unlikely to be fit, leaving Chris Smalling, Victor Lindelof and Eric Bailly, who returned at Huddersfield after 3-1/2 months out with an ankle problem, as his only fit centre backs.
"Marcos Rojo, Phil Jones, Marouane, Zlatan - I don't think they have any chance, so we arrive at this crucial moment with some problems," Mourinho added.
"I think mentality is very important. And we have a strong team, strong bonding, strong team mentality. We know it is a very difficult match - but we go for it."
United have a Premier League clash with champions Chelsea at Old Trafford four days after their European assignment in Spain.
Victory for Antonio Conte's Chelsea side would move them level on points with second-placed United with 10 matches left.
(Reporting by Hardik Vyas in Bengaluru; Editing by Ken Ferris)
