An entertaining London derby saw Arsenal run out narrow 3-2 winners over Chelsea in the first leg of the Carabao Cup semi-final.
The Gunners were 2-0 up and seemingly out of sight by the midway point, but the deficit was halved by Alejandro Garnacho off the bench, who added a second late on to give the Blues hope of reaching the final.
Mikel Arteta's side had the better chances in the match and had potential for more - particularly from set pieces - but there is no immediate need for panic ahead of a second leg at the Emirates.
As for Liam Rosenior, there will be praise for his side's desire to stay in the game and restrict their opponents from long periods of dominance, but questions will be asked of the defending at points - as a win could have been possible on a different day.
Story of the Match
Liam Rosenior couldn't have asked for a better first game in the Stamford Bridge dugout - a cup tie against one of Chelsea's fiercest London rivals.
He would be without several key players - including Cole Palmer, Reece James, Malo Gusto and Liam Delap - but again praised the depth in quality at his disposal, with several players keeping their places from the previous match.
Mikel Arteta, on the other hand, was aiming to keep his side competitive in every competition; he named a very strong lineup despite recent worries over squad fitness.
It would be his side that took the lead after only seven minutes: goalkeeper Robert Sanchez was left in no mans land from a corner as the ball found its way to an unmarked Ben White. The England full-back made no mistake from close range and gave his side the best possible start.
It had taken Rosenior's side some time to find their groove in their FA Cup victory against Charlton, and they were having similar woes here. A fantastic press by Arsenal left the Blues jittery in their own half, and any attempts on goal came via quick counter-attacks.
Though, as the first half progressed, the home side did grow in confidence. Pedro Neto showed brilliant skill down the left wing to get the better of two Arsenal defenders. His low cross failed to pick out a blue shirt in the middle, but it would have been exactly what Rosenior wanted to see from his players.
Another chance saw a misfired effort from Joao Pedro bounce across the width of the Arsenal goal. Marc Cucurella was well placed to turn the ball in, but the Spaniard remained rooted and didn't react in time.
The Gunners had been dangerous from set plays early on, but had started to sit back somewhat after the opener, and could afford to be more patient and cautious with their play - whilst also applying the same level of physicality in their marking to prevent clear cut chances.
Leandro Trossard was a real threat down Chelsea's right flank, and was getting the better of an unsure Trevoh Chalobah; often left to cover defensive duties whilst the full-back Acheampong advanced higher up the pitch.
As half-time approached, it was arguably the away side who held the better chances, despite a respectable push back into the game from the Blues. William Saliba found room for a curled effort just outside the box, which landed on the roof of the net.
There was opportunity back into the game for Chelsea, but they would need to be careful: Estevao found himself going into the book for dissent, while Marc Cucurella - who had just returned from suspension - picked up a yellow for a bad tackle.
The second half was a near repeat of the first - as Arsenal doubled their lead with another early goal, after yet another mistake from Sanchez. Saka had found space down the right and sent in a cross which slipped through the grasps of the Chelsea keeper, gifting Viktor Gyokeres an easy tap-in.
It was a sucker punch for the Blues, who had kept possession nicely in the early minutes.
Big changes were needed to get back into the game, and Rosenior opted for a double change not long after the goal; Benoit Badiashile and Alejandro Garnacho were both introduced.
The swaps proved effective, as just four minutes later Chelsea had a way back into the game through Garnacho, who hung at the back post to smash home Pedro Neto's crossed delivery and rev up the home crowd.
Fernandez had done well to drive the ball through Arsenal's midfield, and Neto was proactive down the right to find space for the chance.
It pinned the Gunners back, too - which allowed for a period of dominance from the home side as they kept possession and momentum in the attacking half.
Things soon flipped, and Declan Rice had an opportunity from a free-kick, but the effort flew well over the bar.
Later, the ball fell to Martin Zubimendi in the box, who was patient and drew in several Chelsea defenders, before placing a shot into the bottom left corner and restoring his team's two goal lead.
It was a big blow for Chelsea, who had struggled to maintain long periods of dominance in the game. The differences between quality in defence was frightening - with Arsenal doing well to cut out several big chances.
The game remained open-ended, however, and following a corner, Garnacho was once again well placed as he struck a half-volley from the edge of the area. It took a bounce off the turf and got the better of Kepa, and gave the Blues a lifeline to try and salvage a draw from this first leg.
The chance never presented itself, despite some last minute efforts from both sides - including a shout for an Arsenal penalty, which would likely have been given if Saka remained in an onside position.
Things turned physical in the dying embers but the Gunners managed to squeeze out the victory, and will be hopeful that their one goal advantage is enough to see them into the final.
Arsenal's performance was stellar as usual - nothing less from a side currently top of both the Premier League and Champions League.
However, it was the introduction of Alejandro Garnacho which kept Chelsea competitive in the game.
The Argentine was well placed for both of his goals, maintaining a high level of energy and intensity that his head coach expects.
Rosenior is particular about his winger profiles, but after two strong performances, he will surely have Garnacho on the top of his pecking order.