Azpilicueta: The Complete Defender  (Sky Sports)

From right-back to left-back to centre-back, Nick Wright examines how Cesar Azpilicueta became the Premier League's most complete defender ahead of Chelsea's clash with West Ham live on Sky Sports on Saturday.

It was three years ago last month that Gary Neville and Jamie Carragher first described Cesar Azpilicueta as the Premier League's best defender. "When I watch him, he's as near to perfect as possible when it comes to defending; he's immaculate," Neville said on Monday Night Football. "You very rarely see anybody get the better of him," Carragher added. "He'd be my number one."

It seemed a big call at the time. Azpilicueta was a largely unheralded figure in a back four which featured John Terry, Gary Cahill and Branislav Ivanovic. But having previously established himself as first-choice right-back, he was proving just as effective on the left, keeping Ashley Cole and Filipe Luis out of the team and helping Chelsea make an unbeaten start to the season.

It had not gone unnoticed by Neville and Carragher, whose comments ring truer than ever three years and two Premier League titles later. Jose Mourinho's back four has become Antonio Conte's back three, and Chelsea's right-footed left-back is now a brilliant centre-back. Since August 2015, Azpilicueta has started 89 league games out of 91. Last season, he did not miss a single minute.

"Last season Azpi was one of the most important players for us," said Conte in September. "In this position as a central defender, he is one of the best in the world. He is very good with and without the ball. He's a fantastic guy, he's always positive, and during the training sessions he works in a fantastic way. For a coach to have him is a dream."

It is extraordinary that a player who had never played at centre-back just 18 months ago might now be considered as one of the best in the world in the position, but the statistics underline why you would be hard pushed to disagree with Conte.

According to Opta, Azpilicueta has only made one error leading to an opposition shot in the last three seasons. None of the eight defenders to have started more than 10 league games for Chelsea in that time have made fewer. Even potential weaknesses have become strengths. Despite standing at just 5ft 9ins, he has won more aerial duels than any other Chelsea player since the start of last season.

Azpilicueta's consistency is invaluable to Chelsea and so too is his leadership. Out on the pitch he can be seen offering constant instructions to Victor Moses - who has described him as one of his biggest influences since moving to right wing-back - and his senior status in the side was recognised when he was made vice-captain in the summer.

Azpilicueta's unflappable style transmits calm in Chelsea's defence but his full-back experience means he is an attacking weapon too. Last season he contributed four assists - more than any other centre-back in the Premier League - and he is already up to five in the new campaign. Only David Silva, Kevin De Bruyne, Leroy Sane and Aaron Ramsey have provided more.

It may seem like a statistical quirk but it is actually the result of a deliberate strategy by Chelsea. Azpilicueta does not get many chances to go on the overlap from his centre-back position, so Conte has harnessed his crossing ability from what's known as the half space, the less congested area between the flank and the centre of the pitch where he is free to launch the ball forward.

Azpilicueta set up two goals from that zone last season, and he has been even more effective since the arrival of Alvaro Morata in the summer. The duo have already combined for five in the new campaign and four of them have come from Azpilicueta's diagonal deliveries from the inside right, with Morata's header against Manchester United perhaps the most memorable example.

Those angled crosses require a target man who is strong in the air and knows exactly when to peel off his marker, but crucially, they also demand a level of delivery most centre-backs simply could not provide. It's why Azpilicueta has made 29 crosses this season, while Chelsea's left-sided centre-backs - Cahill, Antonio Rudiger and Andreas Christiansen - have only attempted six between them.

It's another example of the completeness which, according to Santi Zuza, a journalist for Spanish newspaper Diario de Navarra, has its roots in his boyhood club Osasuna. Zuza was covering their youth teams during Azpilicueta's emergence more than 10 years ago, and remembers a humble teenager with the aptitude and attitude to play anywhere.

"It might surprise people in England but Azpilicueta played as a striker in Osasuna's youth teams," Zuza tells Sky Sports. "After that he became a winger, and when he made his debut in the first team, the manager, Cuco Ziganda, saw that he could do very well as a full-back, a position which demands fit players capable of defending and attacking and making good crosses."

Just as he would at Chelsea years later, Azpilicueta mastered each new position with ease. "He has always been a player with an enormous ability to adapt," says Zuza. "He's smart, he understands the game well and, like all players from Navarra, the region where Osasuna are from, he has a great capacity for sacrifice."

Zuza cites Arsenal's Nacho Monreal, Bayern Munich's Javi Martinez and Newcastle's Mikel Merino as other exponents of those Navarran traits. "The region has a lot of quality players for such a small place," he adds. "It's because Osasuna do good work with their cantera but it's also because Navarran players always have special characteristics."

No one typifies those special characteristics quite like Cesar Azpilicueta. The teenaged striker from Osasuna's academy is now a two-time title-winning defender who can do it all. And the good news for Chelsea is that he is still finding ways to improve.