Arsenal v Chelsea

Before every Arsenal fixture, we’ll bring you a Scouting Report on the Gunners’ next opponents.

Arsène Wenger's side host Chelsea at Emirates Stadium on Sunday. To find out more, we asked tactical expert Michael Cox.

MICHAEL COX

Amid much talk of Chelsea’s 'wobble' in the second half of this campaign, it’s worth remembering that Jose Mourinho’s side haven’t actually lost since a 5-3 defeat at Tottenham on New Year’s Day.

For any other club, a 12-match unbeaten run at this point of the campaign would be considered highly respectable, and Chelsea’s 'wobble' has been about performances rather than results.

A subtle but crucial change to Mourinho’s system caused a defensive shift midway through the campaign. For the first 15 Premier League matches, Cesc Fabregas was used in a deep position alongside Nemanja Matic, and was given license to drive forward into attack, running in advance of attacking midfielder Oscar to provide a stream of assists. Mourinho’s Chelsea were attack-minded, fluid, and unusually exciting in possession.

Since then, however, it’s been rare to see Fabregas deployed in that role. Instead, he’s been shifted forward to the top of the midfield triangle, with Mourinho using a more defensive player, sometimes the energetic Ramires and occasionally the converted centre back Kurt Zouma, to sit alongside Matic.

Oscar has rarely started, Chelsea have been more combative in midfield and the Blues are now more like they were in Mourinho’s first spell at Stamford Bridge: cautious, efficient and resilient.

As ever, Mourinho’s team is based around a fearsome, settled defence, which has brought 15 clean sheets in 32 matches.

John Terry has been an ever-present, and has enjoyed his best campaign for years. He’s protected ably by Cesar Azpilicueta, a right-footed full back who has excelled on the left to the extent that Filipe Luis has been unable to shift him following his arrival from Atletico Madrid last summer.

Gary Cahill and Branislav Ivanovic have also been regulars, and alongside Terry boast a great threat from set-pieces: that trio have managed 15 goals between them in all competitions.

Going forward, in stark contrast to Chelsea’s problems up front last season, Diego Costa was banging in the goals before Christmas. Costa is so dangerous because he’s an all-rounder, capable of using his pace to run the channels, or remaining in the box for crosses. Costa is expected to miss out so Didier Drogba could start - he is still a fine target man but lacks the acceleration of his peak years.

On the wings, Mourinho has found a good balance. Right-sided Willian is a typical Mourinho wide player: hard-working and defensively disciplined. He hasn’t contributed a great deal in the final third, but his discipline allows left-sided Eden Hazard to play something of a free role.

Probably the Premier League’s outstanding player this season, perhaps only Alexis can rival Hazard as an attacker capable of scoring, creating and dribbling so effectively. Hazard’s 13 league goals have come in 13 different games, and that consistent, understated excellence sums up Chelsea in the second half of this campaign.