• Right-back has ankle injury and been playing with pain, manager points out • Wenger believes it is not ideal Bellerín plays for Spain Under-21s in June

Arsène Wenger believes the anger directed by Arsenal fans towards Héctor Bellerín in the debacle at Crystal Palace last Monday was unfair on a player who has battled an ankle injury for much of the season.

Bellerín was in outstanding form until early November, when the problem forced him out for five weeks, and he has not been able to recover his rhythm. At no point since his return to the team on 10 December has he played a game at more than 75% of his fitness levels.

The right-back endured a torrid time in the 3-0 defeat against Palace, although he was not the only one, and when he walked over to acknowledge the travelling support at full-time he was jeered.

Arsenal’s defeat was damaging to their hopes of salvaging a top-four finish and before the visit to Middlesbrough on Mondaynight, Wenger talked of a downbeat mood at the club. Bellerín is among the players who must emerge from the gloom. The Palace result meant that Arsenal have lost four consecutive away games in the Premier League and they have conceded three goals in each of them.

“Was the fans turning on Bellerín unfair? I think yes, as he is a guy who is genuinely Arsenal and wants to do well,” Wenger said. “He is ready to play with pain and I think it is [unfair], yes.”

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Wenger is not exactly thrilled that Bellerín is poised to feature for Spain at the European Under-21 Championship in Poland in the final two weeks of June but he accepts that the player will do so. Bellerín is desperate to be involved. “It’s not ideal after a long season,” Wenger said. “He should have a rest and prepare for next season. The Spanish players love to play for their country and I think he will go.”

Bellerín’s ankle problem has niggled him for some time and two years ago, surgery was a consideration. At the moment, that is not under discussion.

“He has not come back to his best level since he has been injured [in November],” Wenger said. “I think for a while he was feeling the ankle. You get bad habits and you forget that your job is, first, to defend and win challenges because you protect yourself a little bit.

“Then you realise you have to come back and I think now he is trying to focus again on what is important – to defend well. After, he can give us that extra bit that is important as well. I agree that, for a while, he was not the Héctor Bellerín we had seen at the start of the season.”

Wenger knows that anything less than victory at relegation-threatened Middlesbrough will intensify the sense of crisis at Arsenal – and the calls for him to depart at the end of the season, when his contract expires. “I’ve learned to focus on what I think I can influence and what is important,” the Frenchman said. “I get in a little bubble and just focus on what I think is important – and not too much what people say, even if I respect the opinions of everybody. I have to dedicate my energy to be efficient with what I do.

“The fans want to be behind the team and the way we respond on the football pitch will decide the attitude of the fans. The fans love the club. It’s a good period to be united and not divided.

“Historically, Arsenal has been about that. There’s no better period of the season to show it than now. The players are focused and they are conscious that they want to respond [to the Palace defeat]. They accept completely that we were not at the level.”