Wenger, whose side play Manchester United away in the Premier League between the two legs of the semi-final, had identified Atletico, Champions League finalists in 2014 and 2016, as the most risky side in the draw. "We have a very good medical staff and he is very serious in his rehab".
Arsenal were on top form in the home leg just a week ago, when Mesut Ozil and Aaron Ramsey turned on the charm to seemingly put the tie to bed in the first leg. The side drawn first will play the first leg at home April 26, with the return leg scheduled for May 3.
"They are a similar kind of club to us", Atletico Madrid director Clemente Villaverde said at the draw in Nyon.
In the quarter-finals, they beat CSKA Moscow 6-3 on aggregate and showed great spirit to come back from 2-0 down and draw in the second leg in Russian Federation.
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Atletico Madrid advanced 2-1 on aggregate against Sporting Lisbon, despite losing 1-0 in the second leg.
"If you look at the game, we were in trouble in the first half".
That switch in formation appeared to work, as Welbeck tucked the ball past Akinfeev after exchanging passes with Elneny - one of two enforced Arsenal changes tonight - with 15 minutes left to play. Asked about the significance of the competition and his manager's future, which appears to be intrinsically linked with the Europa League, Lacazette replied: "It will save our season because in the Premier League we are not doing well".
If Arsenal are to win the Europa League, they'll need to get past tournament favourites Atletico Madrid in the semi-finals.
Playing each Thursday in Europe and then Sunday in the Premier League has taken its toll on many English clubs over the years.