Manchester United manager Jose Mourinho has revealed he left out Wayne Rooney from his 20-man squad to face Feyenoord due to fears over his workload. Mourinho has taken a star-studded squad to Rotterdam for the opening match of United's Europa League campaign — but Rooney is a notable omission.

Speaking ahead of the game in Holland, Mourinho said he felt it was time to give the 30-year-old forward a rest. He also revealed that Rooney — whose on-field performances have been widely criticised this season — took the decision in a "professional" manner.

"Wayne took it in a professional way," said Mourinho, according to The Mirror. "He's played every game since the beginning of the season, he played also 90 minutes for England and he played 90 minutes last weekend.

"I want him to be fresh for the next Premier League match and at the same time it's the kind of attacking position where I have a lot of solutions and where people are working hard to have a chance."

The United boss has also rested Antonio Valencia and Luke Shaw for the Feyenoord tie. But Mourinho has faith in his other options at full back and confirmed Argentina international Marcos Rojo would start the match.

"Antonio Valencia and Luke didn't travel with the team, they are positions where I have other solutions where I prefer to have fresh players for this game and for the game at the weekend," he said. "We play at midday on Sunday, so I try to have a strong team here and a strong team, Sunday."

The United manager added: "[Rojo] is working really hard, my options in the Premier League in the last four matches were always Luke, Luke, Luke, so I think it's time for Marcos to play — a simple decision."

Meanwhile, Mourinho — who also confirmed defender Phil Jones will be out for a month with knee ligament damage — admitted United would much prefer to be competing in the Champions League, rather than the Europa League. But the Portuguese has pledged to take the competition seriously.

"This is not a competition Manchester United wants, what I want, what the players want, but it is a competition where we are, and that is the reality, so we have to look at the comp with respect," the United boss confessed. "We want to do well in the competition and for a club of our stature, to do well is not to go out of the competition at the group stage."