"When you are playing football, when you are playing in competitive matches, it can happen".
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. We don't want it, but this is our profession".
"His commitment with us is very big. The game in Lisbon was also hard but we won and now we can say those three points were very important". He's helped us with his behaviour, with his quality and his capacity.
Welbeck, who scored the winning goal in the reverse fixture in Portugal, was replaced by Pierre-Emerick Aubameyang in the 29th minute of the game.
Oil tanker & Norwegian Navy frigate ‘collide’ off country’s coast, 7 reported injured
The warship is now in danger of sinking, while the tanker, named the Sola TS , is slightly damaged and did not spill oil. The shipping site Sysla reported that the tanker had been loaded with crude oil and was on its way to the UK.
Welbeck's England and former Manchester United team-mate Jesse Lingard also sent his best wishes through Twitter, saying "Get well soon brother".
But Arsenal could not take advantage as Aubameyang blasted the resulting free-kick well over the crossbar.
He added: "Our mind is to be first in the group".
"Against Liverpool we played a good match, but it isn't enough - we need more".
However, they have not lost since, are fifth in the Premier League, have won all three of their Europa League games and are into the quarter-finals of the Carabao Cup. In our game plan we know we had to be rigorous and they were nearly flawless on that.