MANCHESTER, England -- Altay Bayindir 's 13th-minute mistake gifted Riccardo Calafiori the only goal as Arsenal beat Manchester United 1-0 at Old Trafford on Sunday .

United were the better side for long periods. Still, despite handing full debuts to summer signings Bryan Mbeumo and Matheus Cunha -- before introducing Benjamin Sesko for the final 25 minutes -- Ruben Amorim's side failed to find the net.

Amorim admitted before kickoff that goalkeeper André Onana was fit enough to start, but opted with Bayindir and that decision backfired as his mistake proved the crucial moment.

Arsenal gave debuts of their own to Martín Zubimendi and Viktor Gyökeres , but never fully got into stride. Patrick Dorgu hit the post in the first half while Cunha was regularly a threat,

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