Everton manager Roberto Martinez claims that Phil Jagielka and John Stones make up the finest centre-back pairing in the Premier League.
The two England internationals started for the Toffees in their 0-0 draw with Swansea City at Liberty Stadium on Saturday, and have only conceded five goals in the league this season when playing together.
"I don't think there is a better pair of centre-backs in the Premier League," Martinez said. "They are improving and John is improving to be able to learn how to perform under the most extreme circumstances."
Stones was the subject of a protracted transfer saga after Chelsea made him their most wanted man, and the Spaniard is impressed by how the 21-year-old has handled himself this campaign.
"When you look at John Stones and the way he performs with maturity, the reason he is allowed to play the way he does is because of the influence of Jagielka.
"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."
Next up for Everton is a League Cup meeting with Reading at the Madejski Stadium on Tuesday, before facing West Brom away in the Premier League next Monday.