He again fielded an under-strength XI in Wednesday's 0-0 draw at Southampton, omitting Marcus Rashford, Michael Carrick, Ander Herrera, Paul Pogba and David de Gea, as goalkeeper Sergio Romero's performance earned them a draw.
That news did little to quell rumours of De Gea's imminent departure, with his appearance against Tottenham last time out possibly his final in a United shirt, but Mourinho moved quickly to confirm the Spaniard is still firmly in his plans.
"We played a good team, a team who tried to win and tried to finish well".
"I have been here seven years and I never saw any detail trying to care about the English teams involved in European competitions. David is top of the world and obviously we want to keep him".
Having denied Gabbiadini after Eric Bailly handled the ball on the edge of the penalty area, Romero also kept out a fierce Dusan Tadic free kick in the second half before United's Anthony Martial hit the woodwork. "I think the first match against (American MLS side) LA Galaxy in preseason", he said.
Mourinho also said some players gave him food for thought ahead of the Ajax game.More news: India Bound Skoda Karoq SUV Unveiled
José Mourinho, United coach I think we worked well, we played well; we could have lost as Romero made some wonderful saves but we could have won as we had probably the two biggest chances.
"We have the Argentina national goalkeeper and the Spanish national goalkeeper - two of the best national teams in the world", Mourinho said.
Southampton manager Claude Puel says the Saints should feel "shame" after their goalless draw with Manchester United. "They showed me that they want to be in the final, they want to be an option".
"I think all of them gave me positive feelings".
"We had two different halves - the first one was without intensity and it was very hard after the penalty because that would have given us the confidence". It's very important as it can give confidence and we needed confidence at the beginning of the game.
"I think we deserved to score".