Everton manager Roberto Martinez is expecting even more improvement from his impressive centre-back pairing of Phil Jagielka and John Stones.

The Toffees have already racked up three clean sheets in the current season, and Martinez believes he has the best central defensive pairing in the Premier League at his disposal.

"I don't think there is a better pair of centre-backs in the Premier League," said the Spaniard in the wake of Saturday's 0-0 draw with Swansea City.

"They are improving and John is improving in being able to learn how to perform under the most extreme circumstances.

"As a footballer you've got a human being who is inside you and the way he has coped with everything that has come his way has been incredible."