LONDON -- With strikers this good, sometimes everything else just takes care of itself. Arsenal have one foot in the Europa League final, and that is in spite of the fact nobody would seriously suggest their old failings disappeared against Valencia. What made the difference was that, not for the first time, their outstanding forward line got them out of trouble -- and edged them closer to a first continental title in 25 years.

There is still a second leg to face at the Mestalla, but Pierre-Emerick Aubameyang's added-time volley, his fifth goal in this season's competition, felt decisive. Valencia faded badly after an excellent opening 15 minutes, and Unai Emery's side should have few fears about what awaits them next Thursday. They could have come away with an even bigger lead but, with Aubameyang and Alexandre Lacazette in this vein of form, further chances should fall their way in Spain.

"Arsenal made the most of their opportunities, their first two attacks resulted in goals," said the Valencia manager Marcelino. He was basically right.

Sloppy defending at a corner -- hardly a new theme -- saw Mouctar Diakhaby head the visitors into an early lead. Off the back of three straight league defeats, Arsenal looked stiflingly low on confidence. But then a rapier-like break saw Lacazette play Aubameyang through before motoring into the box to roll his strike partner's square pass into an empty net. Then Granit Xhaka crossed deep, Lacazette's free header squeezed over the line and Arsenal, without really needing to impose themselves on the game, were in the box seat.

"They have two very good strikers; I don't know how many millions of euros they cost," Marcelino said. "You make the slightest mistake at this level and players of that quality can take advantage."

That is what it came down to in a generally low-standard game that, when set against the Champions League semifinals that preceded it this week, was a stark reminder of the difference between the competitions. Arsenal's back line would, with the exception of the excellent Laurent Koscielny, be ravaged at the sport's highest level; their midfield would look ordinary, as it did for long periods here. But their front men would grace that stage and, if Arsenal are to return there, they surely need to be dovetailed without interruption for what remains of this season.

In the round-of-16 win over Rennes, it was a brace from Aubameyang that turned a 3-1 first-leg deficit comprehensively around. Against Napoli a fortnight ago, Lacazette, in the hotbed of Stadio San Paolo, whipped in the free kick that put Napoli's challenge to bed. At this very stage of last season's competition, Lacazette put Arsenal briefly ahead against Atletico Madrid.

They are the only players in this squad who can consistently impact upon high-stakes games like these; they have now scored 43 goals between them this season and, while Emery rotated them heavily earlier in the campaign, they have started five of the past six games for which they have both been available. The Arsenal manager appears to have clocked that their best hope of Champions League football via the domestic or European route is to give his sharp shooters as much cumulative pitch time as possible now.

That looks particularly wise when Arsenal are so vulnerable under pressure at the other end. Dani Parejo forced a save from Petr Cech shortly after Diakhaby's goal and the keeper was sharp, too, to block from the substitute Kevin Gameiro in the second half. There is still a sense that, should Valencia turn up the tempo in the return fixture, Arsenal might find themselves in trouble; in their favour, though, is the fact that the La Liga side looked so ordinary on this night.

"It will continue to be very difficult; I consider it 50-50 for the two teams," said Emery, who admitted surprise that Valencia fielded a three-man back line with Diakhaby, usually a defender, holding in front. Arsenal got around that by using the pitch's width and it was Sead Kolasinac, enjoying plenty of second-half space, who set up Aubameyang's strike with a well-weighted cross. Emery and his players responded superbly to adversity, as they so often have in this competition; they now have only two hurdles to clear.

"It's not normal for Valencia to concede three goals," Emery said. He was right: only Atletico Madrid, just over a fortnight ago, have breached them that many times this season. But they have rarely faced strikers as clinical as Aubameyang and Lacazette, who covered up a multitude of Arsenal flaws while laying Valencia's painfully bare.