MANCHESTER -- John Stones is likely to be ruled out for several weeks after leaving Old Trafford on crutches after damaging ankle ligaments in Everton's 2-1 defeat to Manchester United.
The defender was stretchered off in injury-time and is set to be withdrawn from the England squad for the Euro 2016 qualifiers against San Marino and Estonia.
The 20-year-old will join Everton's lengthy injury list, with Sylvain Distin, Seamus Coleman, James McCarthy and Ross Barkley already sidelined.
"It is a problem with his ankle," manager Roberto Martinez said in his news conference. "It is such a massive blow because he plays with an incredible arrogance and a great maturity and is a very good young player and is going to be a top player. We will assess him in the next 48 hours.
"We need to get the medical department to assess it but it will be at least a few weeks. I don't expect John to be fully fit for next week."
Martinez also criticised referee Kevin Friend for not stopping the game so Steven Pienaar could receive treatment in the build-up to United's winner, scored by Radamel Falcao.
"The referee made a big mistake," the Spaniard said. "Steven Pienaar receives a knock and has to come off. He goes to ground, the ball is in front of him and the referee is well aware and talking with fourth official and I just don't understand that decision.
"Manchester United attacks and the ball ends up in our net and I don't think that is fair."
Martinez defended Leighton Baines, who missed a penalty in the Premier League for the first time, and praised United keeper David De Gea, who saved his effort and injury-time shots from Leon Osman and Bryan Oviedo.
"Leighton Baines is a magnificent penalty taker," he added. "David De Gea was outstanding and [made] two saves that are eye catching but throughout he was very strong and secure. Everyone in the ground was waiting for the net to bulge. He stopped us having a positive result."