Jan Oblak
Jan Oblak was linked with United during the summer. Reuters

Atletico Madrid are desperate trying to keep their most important players by increasing their release clauses following summer approaches by big European clubs like Chelsea, Manchester United, City and Barcelona.

Spanish publication AS claims the club recently improved the contracts of Antoine Griezmann, Koke and Diego Godin at the Vicente Calderon to ward off the Premier League giants and expects to do the same in the coming weeks with United goalkeeper target Jan Oblak.

The La Liga side have seen a number of players like Diego Costa, Sergio Aguero and Radamel Falcao leave the club in recent seasons. But after Diego Simeone kickstarted a new era of success at the Vicente Calderon -- winning La Liga in the 2014-2015 campaign and reaching the Champions League final -- the club are now eager to keep their major assets away from the interest of the bigger clubs.

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AS says Atletico were unable to prevent the departures of players like Diego Costa or Filipe Luis to Chelsea last summer, but have managed to do it this transfer window after all Godin, Griezmann, Koke and Oblak were all tempted to leave the Calderon. The Spanish publication claims that City tried to secure the services of the Uruguay international centre-back after meeting his £29m ($44m) release clause. Atletico, however, reacted on time by improving his contract with a pay rise and setting his buy-out at £42m – with City manager Manuel Pellegrini then signing Nicolas Otamendi instead.

Koke, who has been linked with Chelsea in recent months, has also seen his clause increased to around £48m amid Barcelona interest in securing his services as a replacement for Xavi Hernandez. Meanwhile, AS claim that Atletico also managed to ward off Chelsea and Bayern Munich interest in Griezmann after increasing his buyout clause to £59m.

The Spanish publication claims that the club are determined to keep this new philosophy ahead of the future. This way Atletico expects to meet with Oblak soon after, according to AS, United asked for his services during the summer transfer window amid Louis van Gaal interest in finding a top replacement for David De Gea.

Griezmaan, when asked about the rumours which linked him with a move to the Premier League during the summer, said: "I read things about people saying I wanted to leave this summer but I'm very happy here and if Atlético want me to stay then I'll be delighted to.

"The Calderón is like my back garden. I feel I'm at home with my people and everybody supports me. We'll go out and give it everything," he said. "I want to score more than 25 goals this season which is what I got last year. I'll work hard to get close to Messi and Ronaldo."