Joshua Zirkzee scored his first goal in Europe for Manchester United but the Red Devils were held to a draw by Real Sociedad to leave their Europa League last-16 tie in the balance.
Dutch forward Zirkzee deservedly put the visitors ahead in Spain 12 minutes into the second half with a low strike from the edge of the box that caught out home goalkeeper Alex Remiro.
But Real Sociedad equalised through a Mikel Oyarzabal penalty, awarded after a review by the video assistant referee for a handball by Bruno Fernandes.
Manchester United will feel disappointed not to have won after they dominated the game for almost an hour, with Andre Onana not having had a save to make before the hosts were given the penalty.
Fernandes had a goal-bound strike cleared off the line by Aritz Elustondo in the first half, while the United captain also sent a free-kick just wide.
But Real Sociedad’s equaliser appeared to unsettle Manchester United and Onana had to dive to his right to palm away Brais Mendez’s 25-yard curler, before Orri Oskarsson prodded wide from close range.
Oskarsson then had a chance to win it deep into added time but Onana pushed away his goalbound effort with a strong left hand.
“One thing that I am sure – they’re anxious to score goals and win games,” said Manchester United boss Ruben Amorim.
“They are doing their best and sometimes they want to do their best, but they’re not deciding the best way in their position.”
The second leg will take place at Old Trafford on Thursday, 13 March.
