The latest chapter in a Premier League title race that refuses to become predictable will be written on Saturday when Chelsea host London rivals Arsenal.

After Arsenal had set the early pace, the title then appeared to be heading inexorably toward Manchester City as Manuel Pellegrini’s side went on a scoring rampage. But as City faulted, Chelsea rediscovered their ruthless efficiency under Jose Mourinho to inspire a sense of inevitability about their march toward the trophy. That, though, was before last weekend’s shock defeat to Aston Villa that has left them just four points clear of both Arsenal and Liverpool, having played a game more. The tightness and capriciousness of the race is summed up by fourth place Manchester City, with three games in hand, now being the favorites.

As there has been throughout the season, there remains a widespread belief that Arsenal won’t have what it takes to get the required results required when it really counts to lift the trophy for the first time in a decade. Yet, while they have wobbled, Arsene Wenger’s side have hung around. And a win at Stamford Bridge at the weekend would mean them having to be taken seriously.

While there has long been a sense of Arsenal being a side easy on the eye but ultimately brittle, they have actually been remarkably consistent this season. In matches against teams outside the top seven they have only dropped 10 points, which compares favorably against all of their three title rivals. When not at their best, Arsenal have shown an ability to win games based on the foundation of the defensive partnership of Per Mertesacker and Laurent Koscielny as well as one of their talented attacking individuals stepping up. That was explicitly true this past weekend when Arsenal were far from their best against rivals Tottenham yet still ground out a 1-0 win courtesy of a stunning strike from Tomas Rosicky.

Their problems have continued to come when they have been required to rise to the challenge against the big teams. Arsenal have been blown away by Manchester City and Liverpool, took just one point from two games against a Manchester United team whose threat was purely a psychological one and were unable to take the initiative against a Chelsea team that came to the Emirates in December only with eyes for a insomnia-curing stalemate.

The contrast could not be sharper with their next opponents. The defeat to Villa was the latest example of Chelsea being unable to breakdown or finish off lesser opponents who operate with stubborn resistance. The unconvincing strikers at their disposal was always likely to be a major obstacle to silverware in Mourinho’s first season back in charge and that’s exactly how it’s proved.

Samuel Eto’o has been the best of the bunch and can still finish expertly as well as link up the play, but so much of Chelsea’s attacking threat is dependent on their attacking midfield trio and especially Eden Hazard. The Belgian has become increasingly consistent, and was excellent in a win over Galatasaray on Tuesday, yet he still has off days. Meanwhile Oscar, such a key player in combining pace, creativity and work rate has struggled of late (although encouragingly there were better signs from the Brazilian against Galatasaray).

Against the big teams, though, Chelsea have achieved every result Mourinho has set out for this season. As he did at Old Trafford, Mourinho got the draw he came for at the Emirates, while he beat Manchester City and Liverpool away. The Portuguese coach then showed his sense of opportunism and tactical acumen by exploiting Manchester City’s gung-ho approach and defensive weakness at the Etihad. Chelsea produced their best performance of the season in what was their biggest game to that stage of the campaign to win 1-0.

A match of similar proportion awaits at Stamford Bridge on Saturday when Mourinho will be desperate to maintain his record of never having emerged second best to long-time rival Arsene Wenger.

Team News

Chelsea: Both Ramires and Willian will be suspended for the clash following their sendings off against Aston Villa. David Luiz returned from injury to take his place on the bench in midweek, meaning that Ashley Cole and Marco van Ginkel are now the only absentees. Cole could well return from a knee injury on Saturday but is likely to only be on the bench against his former club. Van Ginkel has returned to training following his cruciate ligament injury and is now set to get game time with the Under-21 side.

Arsenal: Aaron Ramsey, who signed a new contract with the club this week, recently suffered a further setback on his return from a thigh injury, meaning he will be ruled out for at least another 10 days. Mesut Ozil and Jack Wilshere still face several more weeks on the sidelines, while Theo Walcott and Abou Diaby are long-term absentees. January loan signing Kim Kallstrom is now available after a back injury and could be included in the squad for the first time on Saturday.