Eden Hazard back to his best and John Terry isn't missed: What we learned from Chelsea vs Arsenal

Chelsea maintained their momentum following their Champions League win in midweek by beating Arsenal 2-0 at Stamford Bridge in a game that saw Gabriel and Santi Cazorla sent off for the visitors.

After a relatively even opening period, Diego Costa proved the controversial figure just before the break when he appeared to strike Laurent Koscielny's face before his subsequent confrontation with Gabriel resulted in the centre-back seeing red for flicking his heel at the striker.

With Arsenal reduced to 10 men, Kurt Zouma gave the champions the lead after heading in Cesc Fabregas' free-kick before things went from bad to worse for the visitors when Cazorla was dismissed for two bookable offences.

Eden Hazard's powerful strike then deflected off Calum Chambers to earn the Blues victory over their London rivals and to get their title defence back on track.

Standard Sport assesses what went right for the Blues and what went wrong for Arsenal at Stamford Bridge.

Three moments decided this match, all went in Chelsea's favour and on all three occasions Arsenal were to blame. The first was the Gabriel Paulista red card. Diego Costa fouled Laurent Koscielny, chested him over then became engaged in a row with Gabriel. The defender should know better: he allowed Costa to get under his skin and reacted. It was a deserved red card, and wholly avoidable.

Then for the goal, Kurt Zouma - the 6ft 3in, 14-stone athlete - was left completely unmarked at the back post. Arsenal were a man down and defensive assignments may have changed, but you can't leave a player of Zouma's stature alone.

The final mistake was made by their captain, Santi Cazorla, who elected to dive in on Cesc Fabregas in a tackle that picked up a deserved second yellow card. It was completely unnecessary and it only made life that much easier for the hosts.

It wasn't a surprise to see Ivanovic in the starting XI, but that made it no less nervy of a nervy decision for Chelsea fans or exciting for Arsenal fans who had seen the division's best right-back crumble into a complete mess in five matches this season. With Alexis Sanchez lining up on his side the Gunners looked to attack early and often down the left.

For the opening 10 minutes it worked; Ivanovic looked vulnerable. He dived into a couple of challenges after arriving late and found himself chasing the Chilean's ghost. But as the game went on Ivanovic grew in stature and before long he had completely nullified Sanchez.

Not only that but where he had looked laboured in getting up the pitch in recent weeks he was a constant outlet on the right and actually provided some dangerous crosses for the first time all season. Much more like it.

The big decision by Jose Mourinho was to drop his captain John Terry, a somewhat harsh decision given the struggles of the players in front of him. Mourinho kept the pairing that performed well against Maccabi Tel Aviv in midweek, Gary Cahill and Kurt Zouma. Like that game in the Champions League, it was again the younger Zouma who outplayed his more experienced partner.

He, of course, got the opening goal but his general play was much better than the England centre-back. Cahill is more eye-pleasing, especially in possession, where Zouma can look a bit raw and rushed, but all the problems that Theo Walcott caused in the early stages was down Cahill's side. He struggled to deal with the pace and movement of the striker, whereas Zouma was able to track him better and had the pace to contain him.

There wasn't much to do after Arsenal went down to 10 men, but Chelsea looked fine without their captain and will likely continue with this pairing, at least until their next defensive collapse (if there is one).

The reigning Player of the Year is another who has started the season badly and, unlike Fabregas, had a bit of a mixed performance against Maccabi. He started this one quietly with Pedro, Fabregas and Oscar seeing more of the ball in the opening half hour.

But Hazard eventually grew to become the game's most influential attacker. He should have been awarded a penalty when he drove at Paulista and was brought down and, after the Gunners went down to 10 men, he was all over the pitch, picking up the ball at will and getting Chelsea onto the front foot.

He may have done better after he rolled Calum Chambers and went through on goal, but finally got a deserved first goal of the season right at the end courtesy of a heavy deflection off Chambers. He has to produce like this regularly for Chelsea if the champions are to have any chance of catching Manchester City.