Griezmann, 26, is Manchester United's primary target once the transfer window opens, sources have told ESPN FC, with the Premier League club prepared to pay his €100 million buyout clause.

When asked if the France international, who is contracted to Atletico until June 2021, could leave at the end of the season, Simeone told AS: "Yes, because there is a release clause and there are no guarantees. From here on in, I don't know what can happen."

Griezmann only signed a contract extension with Atletico last June, turning down a move to Paris Saint-Germain in the process, after getting assurances that Simeone would remain at the club.

"I spoke to him in the summer holidays, we spoke a lot and he stayed," Simeone said. "He told me that he would stay if I stayed. He then spoke to his agents to sign the [contract] documents."

The attraction of continuing to play for Simeone may be enough to keep Griezmann at the club, though the Argentine says he would never force his player into a decision.

"Griezmann would never allow me to demand of him to stay," Simeone said. "I didn't do it with [Diego] Costa and with [Radamel] Falcao. The players that have given me their lives, I obviously accompany them in the decisions that they take. What is clear is that as long as [Griezmann] stays, the team and the club will continue to grow."

Griezmann scored 32 goals in 54 club appearances last season as Atletico finished third in La Liga and runners-up in the Champions League. He was also the top scorer with six goals at Euro 2016 as hosts France ended up runners-up to Portugal.

Antoine Griezmann signed a new contract with Atletico Madrid last summer.

Griezmann has scored 22 goals and set up 11 more in 40 starts for Atletico this season.

"Great football players want to compete in the Champions League and fight until the end and Griezmann is a great football player," Simeone said. "He is the player that most quickly interprets the team's attacking options. You give him an order and he follows it immediately. He doesn't lose time. He is incredible."

Asked if that could be considered robotic, Simeone said: "On the contrary, he is very intelligent. More than all that he gives to the team, he reads well where we have to attack in a game."

Atletico, who are fourth in La Liga and will take on Leicester City in the Champions League quarterfinals, have also benefited from the good form of Fernando Torres.

The former Liverpool and Chelsea striker, whose contract with Atletico expires this summer, was voted by fans as the club's Player of the Month for February.

"I'm very happy with Fernando," Simeone said. "You see him in training and he trains better than the youngsters. I've never given Torres any gifts. All that he has achieved here, he has earned it through his efforts and hard work. You have to take your hat off."

Torres, who made his Atletico debut at the age of 17, has scored seven goals in 31 appearances in all competitions this season.

Cadena Cope reports that just as he achieved last season, the 33-year-old has already met the requirements previously agreed with the club to earn an automatic one-year contract extension.