Casemiro beaten
The Brazilian was making his first start in almost a month, and his first since arriving at Old Trafford.
Despite coming up against opposition he knows well from his long stay at Real Madrid, the 30-year-old looked to be struggling to get up to speed at times. Too often he would take the easy pass on or give away possession cheaply. He certainly looked off the pace for a good while.
There was one moment in particular he will want to forget. Early in the contest Sociedad's left-back Aihen Munoz pulled off an audacious nutmeg that had Casemiro beaten all ends-up. It didn't get much better after that and the hope among United fans will be that it is just teething problems. Given the good form of Scott McTominay right now, Casmemiro will know he can ill afford to put in too many below-par showings like this if he is to justify the huge £70m spent on him.
Read more: How we rated United's players in Sociedad defeat
Ronaldo shows his frustration
It is now eight United games without a goal for United for Cristiano Ronaldo. He thought he had broke his duck towards the end of the first half here, with a superb, trademark header that just crept over the line. But the flag was quickly raised for offside and he couldn't hide his disgust.
Earlier he could be seen mouthing incredulously after a teammate failed to play him in, while his first touch was just a fraction off the pace when he was picked out beautifully by Christian Eriksen. The longer his drought goes on, the more it is clearly getting to him.
Harsh booking for Martinez
Amid all the hullaballoo and anger that came with the awarding of Sociedad's penalty, it almost went unnoticed that Lisandro Martinez was actually booked for the incident too.
Replays clearly show the ball ricocheting off his knee and up onto his arm - which was moving away from the flight of the ball. To say it was a harsh penalty would be an understatement but the caution for the Argentine was even more ludicrous.
Talk about adding insult to injury.
Sombre backdrop to the match
The mood pre-match, quite understandably, was sombre and low-key. The players were led out without the usual Europa League anthem playing over the speakers and the crowd were largely hushed.
Both sets of players donned black armbands and flags outside Old Trafford were flying half-mast in respect. There was also a minute's silence prior to kick-off and it was impeccably observed by everyone inside the stadium, with Sociedad supporters holding aloft their scarves. It was so quiet that you could hear a pin drop inside Old Trafford on what was a sad, strange and subdued night.
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