John Stones
Everton defender John Stones is a summer target for ChelseaGetty

Chelsea are reportedly keen on signing Everton youngster John Stones, who has formed a strong partnership with Phil Jagielka at the heart of the Toffees defence.

According to the Daily Mail, Jose Mourinho is a big admirer of the English defender and will try to sign him during the summer transfer window.

Stones has grown into a mature and composed central defender since his move from Barnsley in 2013. Apart from playing as a centre-back, the youngster can also play at right-back, and that is a quality that has attracted the interest of the Chelsea boss.

The Blues manager is actively looking for a player, who can be a long-term replacement for John Terry, who is in the twilight of his career. Stones also qualifies as a homegrown player and that will also be in the Portuguese manager's mind.

The 20-year-old defender has formed a formidable partnership with Jagielka at the heart of the Everton defence and put in a assured performance during the Merseyside club's recent 3-0 win over Manchester United.

Apart from Stones, Chelsea are also monitoring his teammate Seamus Coleman, who has performed consistently for Everton at right-back in the last couple of seasons.

However, Roberto Martinez is reluctant to lose his top stars in the summer and has revealed that the club will do everything they can to hold on to their main players.

But has made it clear that they will not retain any player that does not want to play for the club, and will use the funds to strengthen the team further.

"I don't want to lose anyone this summer. We have worked hard last summer to have continuity and our focus is to add two or three to the group," Martinez said, as quoted by the Mirror.

"But in the same way, if someone doesn't want to play for Everton, we need to be in a position where we can become stronger at the end of it."

"It's not down to individuals. I don't want to sell the dream 'oh we need to keep these players' because that's not modern football," the Everton manager explained.

"If you lose a player, you need to become stronger at the end of it by investing well and the recruitment needs to be right," he added.