Wayne Rooney has given the clearest indication yet that his 13-year career at Manchester United will end this summer, with the striker admitting he has to leave Old Trafford to play more.

Rooney has lost his first-choice status this season and has also struggled to make the match-day squads selected by the manager, José Mourinho.

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Asked about his future, Rooney said: “Would I like to stay? I’ve been at this club 13 years, but I want to play football. Here? Of course. I think football changes. You have different challenges in your career. This season I haven’t played as much as I would have liked to. I’ve tried to help the team on the pitch and off the pitch. I haven’t thrown my toys out of the pram but I’m a football player and I want to play football. The more I play, the better, and the more I feel I can help the team.

“Of course you want to play. You want to play every game. Sometimes that’s football and I’ve had to keep working and try to take my chance. That’s what I’ve done. When called upon I’ll try my best to help the team.”

Despite being dropped by Mourinho, Rooney backed him to bring sustained success to the club as they prepare to face Celta Vigo in the second leg of their Europa League semi-final at Old Trafford on Thursday night.

“I said in October, November, that this club will be successful under José Mourinho having seen the way he works,” said Rooney. “If we can win the Europa League, that will be three trophies in his first season. We’re not far off challenging for the Premier League and I hope next season in the Champions League. But I feel the club will be successful under José.”

Rooney has won five Premier League titles, the Champions League, the FA Cup, three League Cups and the Club World Cup. Yet with his future in doubt, the 31-year-old refused to state if the Europa League was a last chance of a major honour with United.

“My focus is on trying to help us win this final and that’s my sole focus. It’s a massive opportunity for us to win a European final,” he said. “I think with Champions League semi-finals, you know you’re in touching distance of the final. This is a European semi-final, it’s the biggest chance to win a European competition in the last two or three years. The tie’s not over. It’s a dangerous position we’re in but we’ve got a good chance of going to the final if we play to our best tomorrow.

“It’s important to be back in the Champions League. This club belongs there. Realistically, it’s going to be difficult to do it through the league. We have to concentrate on winning the trophy.”

Rooney’s United career began with a hat-trick in the 6-2 victory against Fenerbahce in the Champions League group game in September 2004. Asked to recall his continental competition highlights, he said: “All the big European nights here under the lights, the big win against Roma [7-1], the 3-2 against AC Milan, my debut was a big game for me. The European nights are different and you can sense the excitement around the stadium.”

Asked if Fifa’s examination of Paul Pogba’s transfer from Juventus to United will affect the midfielder, Mourinho said: “The answer is simple. No.”

Meanwhile, Mourinho had a clear message for United’s players if they fail to qualify for the Champions League: it will be a reality check and show precisely where the side’s development is at the close of the Portuguese’s first term in charge. Asked how vital Champions League football is to the team’s evolution, he said: “If we don’t qualify for the Champions League, it is because we are not good enough. For the prestige and the finance, Champions League is Champions League. For myself and the players, Champions League is Champions League. If you are not there, it is because you are not good enough. “If we do not go to the final, if we play in the Europa League next season, it is because we are not good enough. If we win, then it means we are strong enough to go to the final. The Champions League is the competition we want to be in. I want to focus on where we are. Nobody has more motivation than I have to try to win tomorrow.”

Despite a gilded history that includes 20 league titles, three European Cups and 12 FA Cups, Mourinho billed the meeting with Eduardo Berrizo’s outfit as one of the most important since the club’s inception. “In terms of motivation, we are even. For Celta, in their words, it’s the most important match of their history and my feelings it’s also the most important match of our history. It doesn’t matter what happened before, what matters is the next one. I don’t believe Celta wants it more than us.

“I am not thinking about myself. I am thinking about the club and I am thinking about the players. For the club it will be very important to be again in a European final. It would be very important to fight for the only trophy the club has never won before. We have a little group with European success. Rooney and Carrick are the English boys who have been a long time in the club plus also there is Mata. No one else did it before. It will be very important for the club and the players. We will fight hard. A long journey. Match number 14 in the Europa League and we are going to fight hard.”

United lost 2-0 at Arsenal on Sunday to leave them in fifth place, four points behind Manchester City, with each having three matches left of the domestic campaign. Mourinho fielded a weakened side at the Emirates with Paul Pogba, Marcus Rashford and Jesse Lingard among those rested.

The 54-year-old denied focusing on the Europa League was a gamble. “The situation is simple,” he said. “Seventeen matches in seven weeks with 16 players is impossible. It was not a gamble. It was a simple decision, based on common sense. It’s completely impossible so since the moment we lost players and initially four of them in one week, Smalling and Jones with the international team and Rojo and Zlatan against Anderlecht, and after that we lost good alternatives, Shaw, Young, Fosu-Mensah, when we lost those it was an impossible job.

“It was not a gamble, it was just a consequence of our situation. We are in this situation and we have to fight for it. Let’s see if we can do it. It doesn’t matter what, no regrets, we are giving everything we can, the players and myself. When you give everything, no problem.”

Mourinho is hopeful the home crowd will make Old Trafford difficult for United’s opponents as he believes it can be an unpredictable venue. “I see a difference between matches,” said the manager. “I don’t think it’s consistent the atmosphere and the enthusiasm. I could in feel the match against Chelsea that they wanted to play from the first minute to the last, it was a very strong Old Trafford. We had a match against Anderlecht where the stadium was not warm enough.

“I hope tomorrow they have the feeling for a second leg semi-final. The only game more important than the second leg of a semi-final is the final. So we have to fight.”

Of how Celta may line up Mourinho added: “I’ve seen [Iago] Aspas play as a nine, on the right, and behind [John] Guidetti. We study the opposition but it’s about systems and principles, no matter what tactics.”