Emery confirmed the injury was "serious" but the Gunners will wait to learn the full extent of the 27-year-old's issue.
As Arsenal wait to find out the extent of the injury, Emery said his players were anxious about their team-mate after the final whistle following a likely serious injury.
One even went as far to say that he had been their worst ever signing.More news: Minnesota, Michigan send first Muslim women to US Congress
Several of Welbeck's team-mates appeared distressed as he received lengthy treatment and needed an oxygen mask. He had some chances too. We think it's a serious injury.
After losing their opening two matches of the season, Arsenal have won 12 and drawn three of their 15 games in all competitions since, including a run of 11 straight victories between August and October.
"The best for him is now to think for the person", Emery said.
Danny Welbeck of Arsenal lies injured during the Europa League match at the Emirates Stadium.More news: Samsung shows off Infinity Flex foldable smartphone display
It remains unclear whether Welbeck will be able to play for Arsenal again before his contract expires in the summer. His injury was hard also for the mentality of the players because they looked at the big injury, but when you are playing football in competitive matches it can happen.
"It's true that I was hoping to score soon, because I came back late from the World Cup and after I lacked a bit of efficiency and luck sometimes", he said. He broke something in his ankle and it's a different injury than another.
Asked what aspect of the game pleased him most, Sarri replied: "The result". They're all big clubs, I was not aware of these rumours, although it's nice, ' Pepe told Telefoot.More news: Eddie Jones Turns On English Media Desperate 'For Him To Be Sacked'