Selection and Overview - Mourinho made one change to his starting team against PSG in midweek bringing Willian in for Ramires on the right flank. Koeman however made 4 changes from the team that beat Crystal Palace the major decision was the selection of Shane Long instead of the desperately out of form Pelle.
The match itself was quite an intriguing contest and a draw seemed a fair result as Southampton were the better side in the 1st half while Chelsea dominated the 2nd. Despite this being a clash between the leagues’ best two defences it was quite an open match with chances at both ends. The fact that there were only two goals in the match was indicative of both teams’ profligacy in front of goal.
Southampton’s Shape - Southampton’s shape was an Atletico Madrid style 4-4-2 with a very narrow midfield line that was given width by the energetic full-backs Bertrand and Clyne. The selection of Long with Mane playing just off him gave Southampton pace in forward areas which Pelle does not offer, but they also provided high work-rate dropping in behind the ball. When Chelsea were building attacks wide men Tadic and Davis would tuck inside and form a horizontally compact midfield line. This was clearly a ploy to attempt to reduce the impact Chelsea’s central players could have on the game by cutting off passing options infield. 
Southampton defended with a mid-block not too determined to press but not sitting back too deep either. Southampton’s 4-man midfield line also posed Chelsea some problems going forward as Willian and Hazard were often required to come inside and prevent their midfield from being outnumbered however when the Clyne and Bertrand went forward they enjoyed quite a lot of space to put whip in a number of dangerous crosses. The main reason Southampton’s full backs enjoyed so much space however was because Willian (surprisingly) and Hazard were quite passive defensively and seemed to be conserving their energy for counter-attacking opportunities.
Chelsea’s response - Southampton were quite successful in initially forcing Chelsea to play out wide. However with players such as Hazard and Willian Chelsea managed to create various dangerous situations from these areas through quick combinations. 
As shown in the image Chelsea created overloads in wide areas to force Southampton to adjust their structure. These overloads forced Southampton to shuffle over and vacate the opposite flank which would create space for other players in this case this was Azpilicueta. This led to Costa’s goal as Southampton focus on being compact was so extreme that no one bothered to mark Ivanovic who then swung in a wonderful cross that Costa simply could not miss.
Chelsea often managed to force Southampton to play the ball back to Forster to play the ball long (ironically) to Long who didn’t get much change off Cahill and Terry. This was more symptomatic of Southampton’s defenders avoiding risks than a well-co-ordinated pressing structure. 
In theory this should have given Chelsea total dominance of possession but they were often second to the 2nd balls after the centre halves won the initial headers this meant that Southampton could build attacks from the midfield area as opposed to always having to start from the back.
2nd Half
Chelsea’s second half dominance was due to a number of factors including Southampton’s decision to sit deeper and focus more on counter-attacking. However this was dangerous given that Chelsea had the game’s outstanding player in Eden Hazard who was capable of receiving the ball from deep and driving through the congested middle of the pitch. Apart from Hazard’s individual brilliance Chelsea only threatened from set-pieces as they displayed an alarming lack of creativity. This can be at least partially attributed to Fabregas’ drop in form whose passing was either predictable or inaccurate. In the second half Chelsea sprayed a number of long range passes from flank to flank as Southampton’s narrow midfield line cut out many passing options in the middle of the pitch. 
The image above demonstrates this perfectly as Hazard comes inside he is confronted by a compact midfield line that are using their shadows to cover the ’10 space’ (red box) in front of their defence. By the time these passes reached their target Southampton shuffled over as a unit quickly to prevent them gaining access to the middle from these areas. Often when Chelsea tried to play through them here they would lose possession and set Southampton up to counter-attack which was obviously very dangerous. Luckily for Southampton in the rare events when their structure was breached Chelsea met Fraser Forster in inspired form who managed to secure Southampton a well-deserved point.
Conclusion - We would expect a game containing the league’s two best defences to be cagey and quite uneventful but that was not the case as both sides used their full-backs as vital extra attackers to overload their opponents’ shape. The result can be seen as good for Southampton (as it is above expectation) and bad for Chelsea seeing as we would expect them to win. However when taking into account that Chelsea are 6 points clear at the top of the table with a game in hand and Southampton are 6 points off the top four the result will be seen in a different light.
Source: DSG
