London - Arsenal took a huge step towards the Europa League final as a double from Alexandre Lacazette and Pierre-Emerick Aubameyang's late strike earned a 3-1 semi-final, first leg win over Valencia on Thursday.

The Spanish side's bright start was rewarded with Mouctar Diakhaby's away goal, but Lacazette quickly turned the game around with two goals in eight minutes before Aubameyang's late intervention gave the Gunners a two-goal advantage to defend at the Mestalla on May 9.

Arsenal boss Unai Emery is a Europa League specialist having won the competition three times when in charge at Sevilla.

And the Spaniard's decision to start Lacazette and Aubameyang together against his former side was richly rewarded despite a terrible start from the hosts.

Arsenal are desperate not just for silverware in Emery's first season but the guarantee of Champions League qualification for next season that winning the Europa League would bring.

A run of three straight Premier League defeats has left Emery's men needing more favours from Chelsea or Tottenham to stand any chance of a top-four Premier League finish.

The Gunners had conceded three times in all three of those defeats to Crystal Palace, Wolves and Leicester and the same defensive deficiencies cost them again early on.

Valencia had already missed a glorious chance to take the lead when Ezequiel Garay somehow turned Rodrigo's driven cross over the bar from point-blank range.

However, the hosts did not learn their lesson and from another set-piece, Valencia took the lead when Diakhaby got the final touch at the back post to force home Rodrigo's header across goal.

Emery has been reticent to start Lacazette and Aubameyang together up front, but the game turned on one moment of magic from Arsenal's two prolific strikers.

Lacazette played in Aubameyang and the Gabon international left his marker and Valencia goalkeeper Neto on the ground before squaring for his strike partner to roll into an empty net.

Seven minutes later, Arsenal led as terrible defending allowed Lacazette a free header from Granit Xhaka's cross and a weak hand from Neto could not prevent the ball crossing the line.

The chances continued to come for Arsenal's front two as Aubameyang volleyed into the ground and over just before the break.

Lacazette then had two glorious opportunities to complete his hat-trick as he firstly failed to connect with an inch-perfect Aubameyang cross before Neto made a brilliant save at his near post to keep the Spanish side in the tie.

At the other end Petr Cech also had to make a smart stop as he raced from his goal to deny substitute Kevin Gameiro.

The veteran stopper has announced he will retire at the end of the season.

And Cech's final game could well be against his former club Chelsea in next month's final as the Blues secured a 1-1 draw away at Eintracht Frankfurt in the first leg of the other semi-final.

Arsenal still have work to do with their terrible away record this season likely to give Valencia plenty of encouragement.

However, they moved much closer to booking their place in Baku when Aubameyang turned home at the back post in the final minute.