To many, Walker was a surprise choice for the PFA Young Player of the Year last season with the right-back pipping Sergio Aguero to the award. Walker's campaign ended in disappointment as Spurs missed out on a Champions League spot and a toe injury ruled him out of Euro 2012. Those setbacks may have played a part in the 22-year-old's performance level plummeting at the start of this season, as Walker committed several glaring errors - such as a costly mistake in the build-up to Chelsea's fourth goal at White Hart Lane - in Spurs' steady start under Andre Villas-Boas. The right-back's form has gradually stabilised, but it still seems as though his strengths lie in the physical side of his game, rather than decision-making and tactical intelligence. There is still plenty of room for improvement.
Evra is not the only defender to divide opinion at Old Trafford, but the left-back's form over the past two seasons has been more of a concern than the gradual progress of Jonny Evans and Rafael, who have both been impressive this year despite Manchester United's poor defensive record. Evra is also enjoying a good campaign after cutting out most of the errors that pockmarked his previous performances and United's vice-captain has also weighed in with four goals and four assists in his 22 appearances. The arrival of Alexander Buttner may have been the boost Evra needed (until he saw the Dutchman play, at least) and the 31-year-old seems to have restored the fans' faith with a string of influential displays. There has still been the occasional boob, but Evra typifies the intent of this United side to beat their opponents by relentless attacking rather than strict adherence to defensive duties. It suits him just fine.
Chico has certainly divided my own opinion since his £2million summer move to Swansea. The centre-back's reckless red card for a dangerous challenge on Louis Saha in September's draw with Sunderland suggested he could be an accident waiting to happen, but since then the 25-year-old has established himself as the Swans' most important defender. Chico's impressive form alongside Ashley Williams has helped Michael Laudrup's side climb to ninth in the Premier League and reach their first domestic cup final, as Chelsea became the first team not to score in a League Cup semi-final since Watford in 2005. Not only is Chico in the top ten for tackles, interceptions and clearances per game this season, he is also careful in his distribution and Laudrup will hope Little Boy Flowers continues to bloom.
Luiz could soon become a midfielder who divides opinion after being moved into the Makelele role by Rafa Benitez at the Club World Cup and the Brazil international has proved the perfect foil to Frank Lampard in his new position. But as Alex Hess says here, much of the criticism levelled at Luiz for his performances in defence has been unfair. The 25-year-old has eradicated most of the errors that caused Gary Neville to describe him as a PlayStation player last season, and he played a key role in Chelsea's Champions League triumph after returning from injury to face Bayern Munich in the final. His future at Chelsea (in terms of where he will play) depends largely on the interim manager's, but whatever happens to Benitez Chelsea have been rewarded for their patience with Luiz, who has now established himself as one of the most important players at the club.
In terms of ability, Koscielny is clearly a better defender than both Thomas Vermaelen and Per Mertesacker. But this season the France international seems to have regressed, with more errors than ever before and a string of unconvincing displays over the past few months. Koscielny's red card against Manchester City summed up his occasional brain fades, and Arsene Wenger should be worried that Edin Dzeko - who is hardly renowned for his movement - managed to get the wrong side of the defender so easily. Arsenal have conceded 17 goals in the 13 league matches Koscielny has started this season and while he is not the only blameworthy defender at the Emirates, the 27-year-old's form remains a concern. He will need to improve quickly if Arsenal are to stand a chance of securing fourth.
Matt Stanger - he's on the Twitter.