Arsenal absolutely dominated their London Derby match against rival Chelsea, scoring three first half goals to win easily 3-0 in the match that celebrated 20 years of Arsene Wenger being their manager. Alexis Sánchez, Theo Walcott, and Mesut Özil scored the goals, but Arsenal's win came thanks to an excellent overall team performance rather than any individual standouts, while Chelsea's defense couldn't get out of their own way for much of the match.
Things started poorly for Chelsea, and they never really got better. They lost possession early and often and struggled dealing with pressure at the back, exemplified by Gary Cahill making an almost tragically poor mistake in front of goal to all but hand an easy goal to Alexis Sánchez and Arsenal 11 minutes into the match. Three minutes later Arsenal were celebrating again, this time after Hector Bellerín, Mesut Özil, and Theo Walcott combined on a picturesque sequence that ended with Walcott snapping the back of the net.
It was obvious that Chelsea were scattered and broken at the back, with Cahill a clear weak point and David Luiz struggling to cover for his partner in central defense. Chelsea would eventually switch to a 3-4-3 to put Branislav Ivanovic on the other side of Cahill to try and protect him more, but that change came in the second half, long after Arsenal had made it 3-0 on a gorgeous counter attacking sequence finished off by Özil and, again, partly with Cahill at fault.
That change in shape did help solidify Chelsea's defense somewhat, even if it was mostly in the form of putting an extra body in the way of Arsenal's attack. Their defenders still struggled on the ball against Arsenal's high press, frequently misfiring clearances and having problems passing the ball around the back, but they didn't concede another goal and were mostly able to shield Thibaut Courtois from having to face as many dangerous scoring chances.
Finally having some measure of defensive solidity allowed Chelsea to get something going in attack finally, but Arsenal's defense held firm, restricting the Blues to just two shots on target all match long. It was a tepid display from Chelsea, and one that manager Antonio Conte will be absolutely livid about for some time to come.
Which team was better from first whistle to last was clear as crystal, and no one wearing blue will be happy about the outcome. Arsenal, however, will be delighted -- not only did they give Arsene Wenger a big win to celebrate 20 years as their manager, they got a win over a loathed rival whom they hadn't beaten in a long time. That made the occasion all the sweeter, and it's a win that will be savored for a long time.
Arsenal: Petr Cech; Hector Bellerín, Shkodran Mustafi, Laurent Koscielny, Nacho Monreal; Santi Cazorla, Francis Coquelin (Granit Xhaka 31'); Theo Walcott, Mesut Özil, Alex Iwobi (Kieran Gibbs 69'); Alexis Sánchez (Olivier Giroud 79')
Goals: Sánchez (11'), Walcott (14'), Özil (40')
Chelsea: Thibaut Courtois; Branislav Ivanovic, Gary Cahill, David Luiz, Cesar Azpilicueta; N'Golo Kanté, Nemanja Matic; Willian (Pedro 70'), Cesc Fàbregas (Marcos Alonso 55'), Eden Hazard (Michy Batshuayi 70'); Diego Costa
Three things we learned
Gary Cahill isn't getting any better
No Chelsea player has drawn more criticism this season than Cahill, and for good reason. The English defender has been in miserable form for most of the campaign so far, making mistake after mistake. The injury-forced absences of John Terry and Kurt Zouma has forced Cahill to stay in the lineup despite his struggles, with Antonio Conte hoping that the veteran could pull himself out of his doldrums, as we've seen him do before.
Cahill was, again, Chelsea's worst player on the pitch by a fair margin. His mistakes were directly responsible for Arsenal's first goal, made their second easier, and then he utterly failed to do anything to make it harder for Arsenal to score on the counter attack that gave them their third goal. He looked like a player that even most managers in the Championship would pass on right now if offered a transfer, and he's been playing like this long enough that there's no way to justify continuing to start him, even with Terry and Zouma still out.
That would mean starting Branislav Ivanovic in the middle with Cesar Azpilicueta moving to the right and Marcos Alonso stepping in at left back, which isn't ideal by any means, but it would also be much better than anything Cahill has given Chelsea this season. Switching to a 3-5-2 later in the match to hide Cahill a bit helped, but Chelsea and Conte still need to find a way to get him off the pitch for their own good.
Arsenal have found their mean streak
In years past, Arsenal have consistently been a very good team but lacked a certain something to be a great team. Many have pointed at needing a better striker or defensive midfielder or whatever else as that missing piece, but above and beyond that was a lack of that certain viciousness to be able to go for the throat at will, and in any game.
Against Chelsea, they displayed that cutting edge, that mean streak that they've lacked before. They didn't settle after scoring once, or twice, or even after going up 3-0. They kept going for more, keeping Chelsea out of the match by keeping them on the back foot, not stepping off the gas at all until very late in the match. It's exactly the kind of ruthlessness that the Gunners have long needed, and it's something fans should welcome.
Now, there's no way to know for sure that this will be a long-term thing. We won't know that until we see it in more matches. But to see it at all is a promising sign, and something that everyone will be watching closely to see how Arsenal build on it.
Hector Bellerín is becoming a very good player in front of our eyes
Bellerín has been an interesting figure for the last couple of years, full of energy and potential but often struggling to put it all together. He'd have one excellent match, but then be utterly anonymous the next. Now 21, the Spanish right back is starting to put things together more consistently this season, and Arsenal are enjoying the fruits of their patience.
Always blessed with explosive speed, Bellerín is starting to learn how to use it more effectively, choosing routes and angles that are as beneficial as possible instead of just running down the pitch really fast. That particular trait was on display when he blazed past Pedro to snuff out a dangerous counter with ease late in the match against Chelsea -- but Bellerín's improvements are about more than just that.
He's also gotten much smarter and more technical about his defending, using better positioning and decision making than we've ever seen from him. That helped keep Eden Hazard quiet for much of the match and has made Arsenal's defense much more solid all year long. If Bellerín keeps up this kind of improvement over the coming months, we could be mentioning him as being among the EPL's best right backs before the season is over.