Manchester United put in a flat performance on a sombre night at Old Trafford as they slipped to a 1-0 Europa League defeat to Real Sociedad. Prior to kick-off, there was a minute's silence to mark the death of Her Majesty Queen Elizabeth II.
The hosts handed a first start to summer signing Casemiro, meaning he was re-united with former Real Madrid team-mate Cristiano Ronaldo. The latter had a couple of half chances that were snatched away from him by good defending early on, with the first real opening falling to Antony, who had a curling effort saved.
At the other end, Mendez flashed a shot just past the post from near the penalty spot, but it was the hosts who did most of the pressing, and they soon thought they had taken the lead when Ronaldo netted with a towering header, only for the celebrations to be cut short as the forward had strayed offside.
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The Portugal international remained the main threat after the break when he sent a fizzing effort from 20 yards just over the bar, while United received a huge let-off as substitute Alexander Sorloth nodded off target from close range.
Sociedad then took the lead just before the hour mark when a penalty was awarded in controversial circumstances for handball against Lisandro Martínez.
Mendez stepped up to take it and tucked the ball right in the bottom corner, leaving David de Gea with no chance.
The visitors nearly doubled their lead shortly afterwards, but this time the keeper was able to beat away a thumping Mikel Merino drive at his near post.
Casemiro headed over from a deep cross as the Red Devils desperately searched for an equaliser, but they found a sturdy defence, who had kept successive away clean sheets, difficult to break down.
Even the introduction of Jadon Sancho failed to spark Erik ten Hag's side into life, with Sociedad keeping their opposition at an arm's length and forcing United to shoot from distance, an invitation Casemiro accepted, only for the goalkeeper to make a comfortable save.
The game became more stretched in the final exchanges and that led to a handful of chances, with Ronaldo seeing another shot deflected out for a corner, while he also had penalty appeals turned away after going down in the box.
Casemiro had the final chance in added time, but a tame, low effort came to Alex Remiro at a nice height, with the goalkeeper making a comfortable save down to his left.
Eventually, Sociedad held on for the victory, extending a good run of form to just two defeats in ten away games, whereas United, who were searching for a fifth successive victory for the first time since April 2021, started their campaign for a second Europa League title with a defeat.
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