Chelsea vs. West Ham United: Tactical Preview of Premier League Game

Chelsea meet West Ham United in a London Boxing Day fixture on Friday. Jose Mourinho will be looking to extend or retain his side's lead at the top of the Premier League table, while Sam Allardyce is looking to further gate-crash the top four.

Let's take a tactical look at this one and see how it may play out.

Chelsea Setup

Jose Mourinho, somehow, has next to no injury worries as he approaches an enticing home fixture against the Hammers. Eden Hazard took a knock late on in the win over Stoke City, but he's expected to play here.

The 4-2-3-1 formation will be rolled out once again, but we'll likely see Cesc Fabregas drop into the holding pivot, allowing Oscar to return to the No. 10 role. John Obi Mikel is the sort of insurance you need on a wet, windy night against the Potters, but not on your home turf when you're expected to take the initiative. 

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Diego Costa failed to score at the Britannia Stadium but looks physically very good, and the Blues will lean on Nemanja Matic in midfield and John Terry in defence. Who Mourinho selects at full-back is anyone's guess; that rotation is impossible to predict.

West Ham Setup

If you'd have suggested this would be a battle between top-four contenders before the season started, you'd have been laughed out of whichever room you were in. Allardyce has done tremendously to right an ailing ship and win the fans' support, buying well, switching formations and getting results.

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Despite the raised expectations in east London, no one genuinely expects this team to go to Stamford Bridge and pull out a victory. That should allow Allardyce a certain amount of freedom, and we hope to see him bring his attacking A-game.

The midfield diamond will be in operation, though with perhaps Enner Valencia in for Diafra Sakho. As good as the Senegalese striker has been, the manager told reporters after the Leicester City victory: "If you don't score in this team, you risk losing your place."

James Tomkins is a slight concern, though James Collins is ready to step in. West Ham will celebrate Christmas knowing Alex Song has not been selected for Africa Cup of Nations duty. Result.

Key Tactical Point 1: Stewart Downing vs. Nemanja Matic

Comfortably, West Ham's best player this season has been Downing. Chelsea have several marvellous, consistent performers, but Matic has been a monster in defensive midfield.

These two are set to go head-to-head, and we're about to see just how good Downing is at working space for himself against a top-class, elite holding midfielder.

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A key part of West Ham's game has been to play a direct ball to Andy Carroll this season, but if that fails, Downing is the first man players look for on the ball. His ability to slip into channels and filter wide to create space for himself has been phenomenal; most opposing teams have wholly failed to shut him down so far this season.

Matic snuffs out most attacks—per WhoScored.com, he's successfully broken up play a whopping 62 times, despite playing on a team averaging 55.7 percent possession—and if he can nullify Downing, the Hammers may be reduced to route one to Carroll fairly quickly.

Key Tactical Point 2: Severe Disconnect?

West Ham's midfield diamond is fairly flat compared to most variations across world football, but against Chelsea it will largely resemble a 4-3-1-2 for most of the match.

Off the ball, Cheikhou Kouyate and Kevin Nolan will have to pull right-back duties and offer protection to their respective full-backs—whoever plays on the right, usually Kouyate, will have to be especially vigilant.

As good as the Hammers have been, and as impressive as their ability to overwhelm opponents has been, this is a Blues side led by Eden Hazard and Diego Costa's piercing runs between full-back and centre-back. Let's be realistic: Aaron Cresswell and particularly Carl Jenkinson are going to relent pretty early without help.

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That's not a knock on them, it's just a reality. Hazard is on fire, Willian is in form and Allardyce's two full-backs are young. They need athletic, committed protectors; Nolan and Kouyate can fulfill the role, but it will create a severe disconnect in the formation.

Carroll and his strike partner will spend long periods isolated, and Downing could struggle to find his way into the game if none of his midfielders are proximate.

*Quote obtained firsthand at Upton Park.