Chelsea's defensive form has not been up to standard this season. They have conceded 27 goals in 25 games, 66 percent of which have come in the second half of matches. Since Rafa Benitez took over, they have dropped points from a winning position on four occasions, drawing with Reading and Southampton and losing to West Ham and Newcastle United.
Their leaky defence has led to them sliding down the Premier League table and missing out on two trophies so far this season, and many are wondering what happened to the defensive philosophy which saw the club secure the Premier League record for fewest goals conceded in a season.
Captain John Terry has been out for long periods of the season after serving a four-match ban and then suffering a knee injury on his return against Liverpool in November. During his absence, Chelsea picked up 14 points from a possible 36, a return which is simply not good enough from a team who were Champions League winners last season.
Deputising for Terry during that time were Branislav Ivanovic, Gary Cahill and David Luiz. At the FIFA Club World Cup, Benitez decided to move David Luiz to the holding midfield role so that he could be afforded more freedom to roam forward without leaving the defence short. This had some success and meant that Ivanovic and Cahill became the first-choice pairing at the back.
Now that Terry is back, Benitez needs to assess what his best back four is going forward into the business end of the season.
Ivanovic marginally has the edge in his tackle success rate with 86 percent to Terry's 85 percent and Cahill's 80 percent. However, the Serbian loses out on pass completion with 93 percent to Terry and Cahill's 96 percent each.
Cahill has made 21 interceptions while Ivanovic has 28 and Terry only 10, although he has played significantly fewer games. Despite this, he has still thrown himself into a tackle as the last man and won the ball cleanly once, something Cahill has achieved twice, while Ivanovic has failed to stop an onrushing striker without cover.
Terry and Cahill are the best pairing when it comes to aerial duels with 71 and 74 percent success rates respectively in 50/50s. Ivanovic and Terry fare best on the ground with 58 and 63 percent of their ground duels won.
After crunching the numbers it is clear to see that John Terry should regain his starting role for the club as he not only provides excellent defensive numbers but an inspirational passion for the club and leadership which cannot be beaten.
What is less obvious is who should partner him.
Despite Ivanovic's superior tackling skills and Cahill's similarities to Terry, it makes sense to start the two Englishmen for the rest of the season. Ivanovic is a natural right-back and whilst Cesar Azpilicueta has done a good job covering the wing, with Chelsea's chances of success this season hanging in the balance, it is necessary to have the best players in their natural positions.
With Cahill and Terry at the back you can be sure that you have two players giving their all to stop an attack, and with the support of Ivanovic and Ashley Cole on the flanks there is a better chance that Chelsea's defensive record will improve by May.
Stats are provided by EPLindex.com