Rúben Amorim’s first major gamble as Manchester United manager backfired when Altay Bayındır’s uncertainty under a high ball gifted Arsenal victory at Old Trafford.

United, who opted against signing a new goalkeeper during their £200m summer rebuild, were forced to start Bayındır with André Onana still sidelined by a hamstring injury. The Turkey international was caught under Declan Rice’s 13th-minute corner, palming the ball only as far as Riccardo Calafiori, who nodded home the game’s only goal from close range.

It was harsh on United, who were the better side for long spells and produced a markedly improved display compared with last season. Matheus Cunha, making his debut, drew three fine saves from David Raya, while fellow newcomer Bryan Mbeumo also went close. Casemiro dictated with a superb passing range, Patrick Dorgu impressed at wing-back and Matthijs de Ligt looked assured at centre-half. Yet, as so often, their failure to capitalise on dominance proved costly.

Arsenal, by contrast, were resilient rather than sparkling, with Rice almost doubling the lead from a free-kick late on. Mikel Arteta’s side have now won five of their past six league meetings with United.

For Amorim, the statistics are sobering. This was his 15th defeat in 28 Premier League games – the fastest any United manager has reached that mark since Paul Hart with Portsmouth in 2009. The applause from the Stretford End at full time suggested supporters recognised the improved performance, but patience is not infinite.

Bayındır’s error underlined the risk of neglecting the goalkeeping position in the summer. Where Peter Schmeichel or Edwin van der Sar once imposed themselves, United now looked vulnerable. Until that fragility is resolved, Amorim’s ambitious rebuild will remain at risk of being undermined by the most basic of shortcomings.