Alexandre Lacazette's brace, coupled with a late finish by Pierre-Emerick Aubameyang helped Arsenal to a 3-1 win over Valencia - who now have it all to do in their Europa League semi-final return leg next week.
They fell behind after 10 minutes, courtesy of Mouctar Diakhaby's header from a poorly defended corner and although initial signs suggested an upset was on the cards, Unai Emery's men duly recovered against a defence-heavy Los Che display.
The hosts might have rued missing so many promising opportunities though, before Aubameyang's late strike doubled their slender advantage - having conceded an away goal which could prove important in next week's return leg at the Mestalla.
Without further ado, here's a look at five things we learned as the Gunners returned to winning ways in their typical hard-fought style:
#5. Goncalo Guedes disappoints in an underwhelming display
Goncalo Guedes, Valencia's club-record signing, was largely disappointing in precisely the type of game they splashed £36m on him for. Call it harsh if you like but the 22-year-old simply hasn't been good enough on a consistent basis this term, after an impressive loan spell at the Mestalla last campaign.
He has netted eight goals and created three more assists across all competitions in 18/19 to date, although eight of those goal contributions (six goals, two assists) have been over the last month. You could argue that dramatic surge of form comes at an opportune time given their lofty aspirations for a successful finish this term - though, individual displays like his on this occasion aren't going to help them get any closer to silverware.
Largely anonymous in the first half, he created one key pass (80.8% pass completion rate) and gradually got more involved after the interval but failed to offer a reliable attacking outlet, committed two fouls and was also dispossessed twice. Against a backline as porous as Arsenal's, he should have done more to continually get at them and cause problems.
#4. Mesut Ozil watch as German continues dividing opinion
After making comments this week stressing he's happy to stay at Arsenal for the duration of his existing contract, Mesut Ozil returned to Emery's starting eleven with another big European game awaiting his presence.
His inclusion was no coincidence: the German playmaker's absence at Leicester last weekend through a foot injury meant he'd have more time to recover with Valencia in town this week, while any "missing" narratives surrounding Mesut were banished after the Gunners' 3-0 defeat at the King Power.
Regardless of his contractual situation and the fact Emery doesn't seem too keen on retaining him in the long-term, it's clear that they perform better with him orchestrating from the number ten role.
He did so again on this occasion - rather subtly at times - but ensured his presence was felt nonetheless. His hold-up play, intelligent movement and spatial awareness were all keys in helping build attacks as Arsenal grew in confidence, particularly for Lacazette's first strike.
Substituted after 73 minutes for an ineffective Henrikh Mkhitaryan, there are still some doubters who believe he's not suited to the "dirty work" and fight attached to away games. Nonetheless, it's nice to see him return with another encouraging showing.
#3. Arsenal's defensive frailties continue to appear again
After a week where they conceded three goals in three successive games, it's fair to say Arsenal's defensive frailties have returned to the fore. Nine goals conceded in three games. Over their last ten matches (all comps) prior to the 3-2 Crystal Palace defeat, they had only conceded six.
Yet the inconsistency at the back has reared its ugly head once more and Unai Emery can only watch as his side continue conceding preventable goalscoring opportunities which ultimately lead to silly goals. Whether they're individual mistakes, sloppy marking from set-pieces, poor decision-making or a combination of all three, the Gunners' defensively has been their Achilles heel for many seasons now and this one is no exception.
Shkodran Mustafi, playing against his former side on this occasion, made a few important interventions but equally performed like a man under pressure. Every time he was near the ball, you could hear the tension from home supporters - aware how his mistakes in particular have cost them crucial points in their top-four race this term.
As for Ainsley Maitland-Niles, he's playing out of position. Predominantly a winger or central midfielder, Hector Bellerín's long-term ACL injury means he has had to fill in and done a solid job at right-back - but not without the odd scare. Sokratis and captain Laurent Koscielny are regularly kept busy but are not without their faults, while the same can be said for Sead Kolasinac - a menace in transition on attacks but defensively suspect against top opposition.
Combine all of that and well, Valencia should've found themselves a three-goal cushion before the 20th-minute mark. Ezequiel Garay missed an open goal, Daniel Parejo forced Petr Cech into a save from distance while Mouctar Diakhaby's headed finish at the near post was painful to watch from a neutral perspective. Questions will continue to be asked of their defence and they're not being answered convincingly.
#2. Marcelino gets his tactics all wrong as Valencia exposed
You can understand Marcelino being wary of Arsenal's threats, particularly with their home advantage and given Unai Emery's Europa League pedigree to boot. However, that's not an adequate excuse to justify why he opted to change his tactics specifically for this game - where Valencia fielded six defenders - and were inviting pressure on themselves for sustained periods in both halves.
Other than a 15-minute spell at the start of both halves, Los Che found themselves swamped in their own area and if not for some wasteful finishing on Arsenal's part, would probably have no chance of recovering their deficit next Thursday.
Fullbacks Gaya and Piccini are both adept at flying forward as well as defending when called upon, so they were both expected to start as normal. But fielding four central defenders, playing one of them in defensive midfield and watching that unfold felt like a mistake Marcelino's men could never really recover from.
Former Arsenal man Gabriel was arguably their best defensive performer and unsurprisingly too, on his return to the Emirates. Argentinian duo Ezequiel Garay and Facundo Roncaglia partnered him in central defence, while goalscorer Diakhaby was shifted forward into a defensive-midfield role.
I can understand him wanting to use the players available at his disposal, but with Geoffrey Kondogbia sidelined and Francis Coquelin suspended, why not start Daniel Wass in midfield as usual? The game was crying out for his presence - not least after Diakhaby's booking 30 minutes in and despite a 20-minute cameo, he was one of their few bright sparks on a forgettable evening.
Now they have it all to do in the second leg next week and it's partly down to Marcelino's baffling tactical decisions, which left their backline under needless levels of attacking pressure while relying on counter-attacks to create chances once the game settled down.
#1. Alexandre Lacazette grabs two but should have had four
Alexandre Lacazette was the Man of the Match and once again showcased why he - not Aubameyang - is their most complete attacking option during this 3-1 victory. With 18 goals across all competitions this season, the pair have now combined to score 43 goals in 18/19. Yet both could have so much more and it ultimately boils down to finishing promising chances when they're presented on a plate.
His hold-up play and ability to create opportunities for others, bringing teammates into attacks, remains an underrated facet of his game. It proved pivotal during the build-up to their first goal, where he combined alongside Ozil and Auba to equalise at a vital time to settle the hosts' nerves.
However, he should have netted a first-half hat-trick and then capped a great performance with more after the break. Aubameyang's floated cross into the box was perfectly-weighted for the Frenchman to convert from close-range, yet he failed to connect with his attempted header and the danger was averted.
Then three minutes later, he saw two efforts in quick succession thwarted by the combination of an alert Neto and Gabriel's last-ditch sliding block. Striking goalwards at Neto's near post, the Brazilian read his effort and snuffed it out dramatically with his outstretched leg.
You could be forgiven for reflecting back twelve months ago, to the first leg of their Europa League semi-final clash with Atletico Madrid. Diego Simeone's side were a man down for nearly 80 minutes and still managed to draw 1-1 while netting a crucial away goal. If not for Aubameyang's stoppage-time strike, they would've been travelling to the Mestalla with a much less comfortable advantage and renewed fear that history would repeat itself twelve months on.