Branislav Ivanovic, one of Chelsea's most consistent players, has played unusually below par recently.
Ever since his transfer to the Blues, from Lokomotiv Moscow in 2008, the Serbian has been a stand-out player across the line of defence, and it's this versatility, composure and awareness of the game which has brought the Champions League and league title back to Stamford Bridge.
However, this season the 29-year-old has, on more than once occasion, been the source of some shaky defensive performances in the Premier League, and importantly in Europe, where Ivanovic twice left Basel's Mohamed Salah open to humiliate Chelsea in both group fixtures.
You'd have thought Serbia's captain would have learnt from his two mistakes, but once again he was caught napping to allow Jay Rodriguez to score a sloppy 13-second goal for Southampton a week ago. Luckily he was bailed out by his team-mates.
The Branislav Ivanovic we remember, scoring the extra-time winner in the Europa League final last season, needs to return if Chelsea want to claim the top spot.
Nevertheless his ambition hasn't grown cold, Ivanovic told Sky Sports that he believes his club have their best chance of winning the Premier League since 2010, the year Chelsea last won the title, under Carlo Ancelotti.
The Italian replaced Jose Mourinho at Real Madrid in the summer, and the latter has stuck by Ivanovic this season, after showing some interest in the defender while in Spain, starting him in 15 games in the league even after a threat to drop the Serb following his sloppy displays.
Although, Chelsea don't have many options at right-back, Ivanovic has said he is a natural central defender, but has been effectively deployed out wide by the numerous managers he has played under.
His loyalty to the Blues of over five years, making Ivanovic one of the longest-serving players at the club, has been rewarded with a starting-place in the majority of games so far, being preferred to the more natural full-back, Cesar Azpilicueta, who's found himself deputising for Ashley Cole at left-back.
Even so, Chelsea could be on the look out for a new defender in January, to replace Ivanovic, who is 30 in February.
St. Etienne starlet Kurt Zouma has been rumoured, along with full-back, Fabio Coentrao, and even Real Madrid's Sergio Ramos is a target.
Whether it's Ivanovic, another player or a hole in the defence which Chelsea want to replace and repair, a new addition does seem essential at the back, as the Blues lost 3-2 to Stoke City on the weekend, to further distance themselves from leaders Arsenal.
If Chelsea seriously want to challenge for the league title, and repeat their 2010 campaign like Ivanovic said, he for one needs to rapidly improve or else he'll have to wait until next season for another Premier League winners medal.
What do you think of Branislav Ivanovic?
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