Meetings between Jose Mourinho and Sam Allardyce are always entertaining, partly because both managers seem determined to wind one another up as much as possible.

Mourinho famously criticised Allardyce’s tactics after West Ham frustrated Chelsea at Stamford Bridge last season, slamming the ‘19th century football’ played by the Hammers.

“He [Mourinho] can't take it, can he?” Allardyce scoffed after the goalless draw. “He can't take it because we've out-witted him. He just can't cope. It's brilliant when you get a result against him. Hard luck, Jose.”

Mourinho should be careful with Allardyce, though – the Chelsea boss once admitted 'Big Sam' was the Premier League manager he’d least like to face in a fist-fight...

A touchline brawl looks unlikely this time around – and so is any criticism of West Ham’s football. Allardyce’s side have changed their approach from last season and developed a more cultured, attractive style of play.

While the former Bolton and Blackburn boss remains a highly reactive manager, and would probably be delighted with another 0-0 at Stamford Bridge, he’ll be reluctant to disturb the harmony in West Ham’s team ahead of the Boxing Day clash.

While forwards like Diafra Sakho, Enner Valencia and the returning Andy Carroll have received much praise, with Stewart Downing also deservedly making headlines too, equally important has been the performances of West Ham’s central midfielders.

There, Allardyce recruited two excellent midfielders in Alex Song and Cheikhou Kouyate, who have impressed with both their physical power and their technical quality. They summarise West Ham’s style of play – they’re more attractive to watch, but they’re still very direct.

Song the string-puller

Song, in particular, is an intriguing player. While initially considered a rather limited defensive midfielder in his early days at Arsenal, the Cameroon international became a more cultured player in his final season, a deep-lying playmaker rather than a pure destroyer. Robin van Persie benefited heavily from his lofted through-balls, and Song’s creative ability earned him a move to Barcelona.

At West Ham, Allardyce has deployed an unusual midfield diamond which features a winger, Downing, as the No.10 , and Song continuing to loft balls forward from deep-lying positions. For example, look at Song’s distribution in the 2-0 victory over Leicester last weekend, and it’s clear he looks forward whenever possible. His square passes are clearly more reliable, but Song remains determined to feed Carroll and Sakho.

You can also break down Song’s distribution in a different way – splitting it between passes played in the midfield, and passes played into the final third. Here’s his passing from the 1-1 draw at Sunderland.

A similar pattern emerges, and Song’s pass completion rate when attempting balls into the box is extremely low. Nevertheless, it encourages West Ham to look for the two strikers quickly, and Allardyce’s teams are always good at winning the second balls in and around the penalty area.

Kouyate the shuttler

Kouyate plays a very different role. He’s the shuttler, usually playing to the right of the diamond and concentrating on getting up and down the pitch, providing mobility.

His display at Sunderland shows, for example, how he made 5 different fouls across the width of the midfield zone, but generally offloaded the ball sideways.

His more ambitious balls were played from wider positions, including one fine pass to Sakho. That was the only ambitious ball into the box attempted by Kouyate – but it was successful, which is more than Song managed, despite constantly trying to force the issue.

These two should be crucial against a Chelsea midfield featuring great power in Nemanja Matic and Cesc Fabregas, and perhaps John Obi Mikel after his good performance in the 2-0 win at Stoke on Monday.

However, Song may also find himself man-marked by the tactically intelligent and hard-working Oscar, who would prevent him from hitting the forwards quickly. It therefore may be Kouyate, given freedom to charge forward from the right of the diamond, who is more useful here.

Either way, both have settled well, and Allardyce will be desperate for both to perform effectively over the Christmas period. The duo will be split up when Kouyate departs for the Africa Cup of Nations in January (Song appears to have been surprisingly omitted from Cameroon's squad) - how they cope during that period will be a good indication of West Ham’s chances of staying in Champions League contention.

Chelsea vs West Ham LIVE ANALYSIS with Stats Zone