Valencia v Arsenal: preview and possible line-ups
After their 6-2 drubbing of lowly Huesca at the weekend, Valencia will likely look to field a similar team on Thursday night. Influential midfielder Geoffrey Kondogbia has returned to training following a thigh injury, but he is unlikely to feature against Arsenal.
Otherwise, only Denis Cheryshev is missing with a long-term knee injury as Marcelino looks to put out a side capable of turning around a European semi-final.
Ezequiel Garay could feature at centre-back alongside former Arsenal man Gabriel, whilst Santi Mina will likely return after missing the first leg through suspension.
Arsenal have no new injury worries for the clash against Valencia, with Aaron Ramsey, Denis Suarez, Hector Bellerín, Danny Welbeck and Rob Holding all out for the rest of the season.
Laurent Koscielny is set to be restored to the starting XI after sitting out Sunday's draw against Brighton, with veteran goalkeeper Petr Cech also likely to start in what will be one of his last matches as a professional footballer.
Marcelino looks to Liverpool for inspiration as he eyes second leg comeback
"Last night's game demonstrates that anything can happen, it's a lesson that tells us that if we play to our maximum we'll have the chance to make it to the final," Marcelino told a news conference ahead of Thursday's second leg at Mestalla.
"It's beyond doubt that we'll have a better chance if Mestalla supports us from the start. We're going to go through difficult moments and we're going to need them.
"We're going into the game with the belief we can beat Arsenal, the players have transmitted that to me and I am convinced we have a chance."
Emery stresses need for illusive solidity but insists Arsenal are going out to win
"We started with two possibilities to qualify for the Champions League.. The league is one. And the Europa League is another. We know it is going to be difficult but we have to have a strong mentality. I want to enjoy it. A difficult team away. It is all positive for us", the Arsenal boss said.
"They have good players but defensively we need to be strong and need to take our chances. 90 minutes can be long. We need to be solid", he continued, before adding: "Our idea is to play the match to win. If you want to win you need to score".
Valencia: Neto; Piccini, Gabriel, Garay, Gaya; Wass, Parejo, Coquelin, Guedes; Mina, Rodrigo
Arsenal: Alisson; Alexander-Arnold, Lovren, Van Dijk, Robertson; Henderson, Fabinho, Wijnaldum; Salah, Firmino, Mané