Rio Ferdinand believes Chelsea boss Thomas Tuchel has turned Antonio Rudiger into the Premier League's best defender.

Rudiger was on the outer at Stamford Bridge under Frank Lampard, who was replaced by Thomas Tuchel in February.

The German has since become one of Tuchel's most important players, and Ferdinand puts him up there with Manchester City star Ruben Dias.

"Frank's respectful and I think he's honest enough to know and would say Tuchel has done an amazing job," Ferdinand told FIVE.

"But at the same time I'm sure Frank's sitting there thinking, 'well I didn't see these certain players performing like this when I was there'.

"But then it's about Frank looking at himself, looking at his tenure there, did he approach things the right way. I'm sure he's doing all this, he's looking at, 'Could I have handled this situation better, could I have handled that player better?

"That's what Frank will be going through and he'll be looking to make sure he rights the wrongs from his time at Chelsea.

"But you can't do anything but respect and pay homage to what Tuchel has done.

"Look at Rudiger, he's arguably since Tuchel has been there [at Chelsea], been the best defender in the Premier League. Him or [Ruben] Dias in that time. He's been unbelievable, he's like an animal."