David de Gea has passed up an opportunity to commit his future to Manchester United, with the goalkeeper’s deal set to expire next summer.

While United have an option of a further 12 months the club are keen to ensure De Gea stays for a lot longer. Yet asked if he intends to remain at Old Trafford, the Spain goalkeeper refused to be drawn. “I feel really loved in this club – from the fans, from all the people who are for this club,” he said. “I am really happy to play for this club, one of best clubs in the world, so for me it’s really good to be part of this club.”

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The 27-year-old’s reaction may cause surprise at United given the confidence last month that he would sign again. While De Gea is thought to want a marked increase on his salary – now around £180,000 a week – he received criticism for some shaky displays during Spain’s World Cup campaign.

“I never listen to stupid things they say,” he said. “Normally I never listen to the people who speak about me. I’m focused on my job and trying to help my team, trying to improve every session and trying to be as good as I can.”

De Gea, who signed from Atlético Madrid in summer 2011, is expected to start United’s Champions League group game against Young Boys at the Stade de Suisse on Wednesday night on an artificial pitch. He is of the same mind as José Mourinho that the surface will make the match more difficult.

“We are not used to playing on artificial grass so it’s going to be a bit different – probably more difficult for us but we have to train there to see how the balls work on this pitch and try to play our football here. We know it’s going to be a tough game,” he said.

Mourinho stated a desire not to use the surface as an excuse for any disappointing result. Yet he hinted he had complained about it at a recent Uefa meeting while also branding it a disadvantage for any visiting side.

“I don’t want to use that especially before the match as a possible excuse for a not very good performance,” he said. “But what I had to say I told last week in Geneva in the Uefa meeting, and what can I say? They play on an artificial pitch, which is a big advantage for them and a big disadvantage for the other teams.”

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Mourinho used the example of Roger Federer to illustrate the requisite mindset his players must adopt. “We are in Switzerland, the home of one of the best ever tennis players, and I’m pretty sure the big man sometimes is not happy to play on such a surface but he has to play and has to win,” he said. “He has a favourite surface but he has to win on the surfaces he is not in love with. We have to do it.”

He added: “With [the club captain] Antonio Valencia we need to protect his clinical situation, apart from that we go with everything we have and have to try to win.”

In Valencia’s absence – the full-back’s knee injury precludes him from playing on the artificial surface – Diogo Dalot, the 19-year-old signed from Porto in the summer, may make his United debut.

“He has a chance to play,” said Mourinho. “I said already that Luke Shaw is playing and apart from him we have Diogo, Ashley Young and Matteo Darmian ready to play.”

Marcus Rashford will start against the side who last season became the Swiss champions for the first time since 1986. Mourinho said: “He’s selected but I just want to remind you we can only start with 11 so when you see the team you could try to speak about the ones that are going to play and not the ones that are not going to play.”