The 27-year-old took on oxygen as he was tended to on the pitch for several minutes before he was stretchered off, with some of Welbeck's team-mates were left visibly distraught by his plight.
"But when he had the injury we needed to play with a right-back which was the reason we played with Ainsley [Maitland-Niles]".
His recent showing came against Liverpool on Saturday when he came off the bench to set up Alexandre Lacazette for Arsenal's equaliser that extended their unbeaten run to 14 matches across all competitions. "The game in Lisbon was also hard but we won and now we can say those three points were very important". They saw it was a big injury. "We don't want it, but this is our profession".
Welbeck is out of contract at the end of the season, and Emery added: "He's a very good person".
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For his confidence I think it is very important". Now we want the second target, to win our group. I think they could draw the match".
"We follow him every match", the Arsenal manager said. He's helped us with his behaviour, with his quality and his capacity. His injury also affected the mentality of the players as they could see it was a big injury.
The game only really opened up in the 88th minute when Jeremy Mathieu was shown a straight red for a foul on Pierre-Emerick Aubameyang as the striker raced through on goal.
Emery said after the game: "Lichtsteiner's injury changed our idea on the match, we wanted to change for Eddie Nketiah and give another chance for the striker".
The incident knocked the wind out of Arsenal's sails but Welbeck's replacement Aubameyang hit the crossbar as the visitors offered very little in terms of an attacking threat. But when the match finishes, the first thing they did was ask for him. We know what we expect from each other, so we're also trying to get the best out of each other in training.