The first leg of was played in Turin due to coronavirus-related travel restrictions on visitors from Britain to Spain during the pandemic.
Fernandes had Sociedad’s defense to thank for his first goal in the 27th, when two defenders collided with their own goalkeeper, leaving him free to score into an empty net. He then finished off a quick counterattack to make it 2-0 in the 57th.
Fernandes let Marcus Rashford’s pass go behind him to Daniel James, then received the ball back and fired inside the right post.
Rashford added the third in the 64th and James completed the scoring in the last minute.
United is playing in the Europa League for the third time in five seasons, a drop for a club once regarded as a continental heavyweight.
Elsewhere, Gareth Bale reminded his detractors of his qualities as he scored one goal and set up another to help Tottenham defeat Austrian team Wolfsberg 4-1 in Budapest, Hungary.
That game was also moved due to coronavirus-related travel restrictions for British visitors.
The Wales forward, back at Tottenham on loan from Real Madrid to the end of the season, cut the ball back for Son Heung-min to open the scoring in the 13th, before he illustrated why Madrid paid Tottenham a record transfer fee for his services in 2013.
Bale showed Matt Doherty exactly where he wanted the ball, outpaced Jonathan Scherzer to reach it, then stopped to leave the Wolfsberg defender sprawling, before curling a powerful shot past goalkeeper Alexander Kofler with his left boot.
Bale has been struggling in his second spell at Tottenham, making just seven Premier League appearances.
He recently irked José Mourinho for posting “Good session today” on Instagram with the Tottenham coach saying there was “ a contradiction between the post and the reality.” (AP)