Manchester United legend, Gary Neville, says he is shocked by the performance of Victor Moses and the quartet of David Luiz, Cesar Azpilicuerta, Marcos Alonso and Gary Cahill in Chelsea's defence this season.
Chelsea head to West Ham on Monday with a 10 point lead over their nearest rivals and edging ever closer to the Premier League title.
But Neville who won the Premier League title, FA Cup, League Cup and Champions League with United during his playing career, says he didn't think Antonio Conte's men would win the league at the start of the season because of the uncertainty in his defence.
"The reason I didn't think Chelsea would win the league this year is (David) Luiz," Neville told express.co.uk.
"Could he settle back into the Premier League, how could he not give goals away, how could he not make mistakes? [But] he's a fantastic player and character.
"Azpilicueta had fallen off in the last year.
"Gary Cahill, you didn't know whether he would partner Luiz.
"Alonso, we've not seen too much of him, he was at Bolton but we didn't know how he would settle.
"Moses is a complete shock.
"Those five had huge question marks about them.
"The fact that they have done well has just shocked and surprised everybody."