Julen Lopetegui is demanding improvement from his West Ham side after their frustrating defeat by Aston Villa.

The Spaniard’s first competitive match in charge of the Hammers ended in a 2-1 home loss on Premier League opening weekend to last season’s fourth-place finishers at the London Stadium, with Jhon Duran - a player West Ham tried to sign earlier this summer - coming off the bench to net a late winner.

Villa debutant Amadou Onana had earlier given the visitors the lead just four minutes into the game after heading in at close range from a corner, before Lopetegui’s side were handed a reprieve before the interval when Matty Cash was penalised for a foul on Tomas Soucek and Lucas Paqueta netted from the spot.

It was a mixed bag of a performance from a West Ham team containing two full debutants in Max Kilman and Guido Rodriguez and three more coming off the bench in Niclas Fullkrug, Jean-Clair Todibo and Crysencio Summerville, with the hosts playing their part in an absorbing second half and twice being denied a share of the spoils late on as Emiliano Martinez saved from Danny Ings and Ezri Konsa made a sensational last-ditch block to deny Soucek a last-gasp equaliser.

However, they looked defensively vulnerable throughout despite an assured debut from £40m signing Kilman at centre-back and should have been further behind by the time of Paqueta’s fortunate equaliser after Leon Bailey hit the post for Villa and John McGinn also fired just wide.

Lopetegui cut a frustrated and animated figure at times both during and after his first game in charge of West Ham.

“The Premier League is the most demanding competition around the world, so the little details are key,” the former Wolves boss said afterwards.

“Today I think that we gave a big effort. We did and that is why we are very unhappy, above all, for our fans, and for the players too, because they made a big effort. It was a pity.

“It’s true that we lost against one of the best teams in the Premier League in the last season, and maybe in the current season too, but I think that despite this, we equalised a very hard match in a lot of moments. In other moments, I think that we overcame them too, but it's about the goals.

“We suffered very early, when we conceded from a set-piece, and we have to improve about this for sure, all these things, because these little details are key. They allow you to take advantage of a lot of good work, and after we equalise the match, I think that we finished the first half better than them, in my opinion, and the start of the second half too. But if you don't score, of course, the match changes.”

“They have a very good team, and in the end, despite that they scored the second goal, we had two very two clear chances to score in the end of the match, but we don't score. We suffered two goals and we scored only one, so we lost. We are very disappointed with this, and we have to keep the good things that we showed and we did, and we have to improve the bad things to be more competitive.”

It was particularly galling for West Ham to see the winner against them scored by Duran, a player whom they explored signing last month before completing a £27m deal to sign Germany striker Fullkrug from Borussia Dortmund.

Duran - also tracked by Chelsea across the last two transfer windows - was criticised by Villa fans last month after appearing to make a West Ham gesture with his arms amid those transfer links during an Instagram live appearance.

He celebrated his winning goal on Saturday by gesturing to the jubilant travelling fans that he intended to stay with Villa going forward.

Villa boss Unai Emery hopes Duran will remain at the club, telling reporters after the game: “We believe in him and his potential.

"We are open to working with him like he did today, helping the team, being available when we need him and today he was fantastic.

"With [Ollie] Watkins not feeling 100 per cent we prepared the plan for today to use both players over 90 minutes.

"Always I am very committed with him to get the best out of him as a player and even as a person. Some mistakes we have to accept and of course not repeat it. At the beginning I wanted him here and nothing changed after the match today.

"We were before, with every player, open in case a big offer comes in, and one of those players is him. But we know his potential and we know if he is leaving the offer is good for the club. But I don't want him to leave."

Quizzed on West Ham’s previous interest in Duran, Lopetegui said only: “I'm not going to talk about individual players of the opponent. Each player helps his team always and he is not our player.

"For sure we are unhappy because we lost at home against a very big team Aston Villa, a Champions League team. When you lose you have to be always sad, I feel it myself we had expectation to give our fans one happy day. It was not.

"We tried and we have to keep the good things we did and improve other things, that's for sure."