Everton manager Roberto Martinez has moved to calm fears surrounding John Stones, after the defender was replaced during their 2-1 League Cup win over Reading on Tuesday.
The defender appeared to be in some discomfort as he limped off early in the second half, but Martinez insists it is nothing serious.
"John was withdrawn as a precaution more than anything. He had a knock in his knee and we couldn't take any risks," the Spanish coach said.
"He will be assessed over the next 48 hours but I don't think it's serious."
That will come as a boost to Martinez, whose side will do battle in the Merseyside derby in two weeks' time.
Everton will arguably have to find their feet quicker than they did at the Madejski Stadium, where they suffered a scare after Nick Blackman's first-half opener.
The class of Martinez's men eventually shone through though, as Ross Barkley drilled home an equaliser just after the hour, before Gerard Deulofeu sealed the win with a terrific free-kick.
While relieved to see his side ease their way into the fourth round for the first time in four years, Martinez admitted his side were given a thorough examination by Steve Clarke's Reading, who will fancy themselves for a promotion push after a promising start to the Championship season.
"You have to give credit to Reading," Martinez said.
"We had to change it tactically so we could penetrate more and get the extra pass.
"Gerard came up with that bit of magic that turned out to be the winning goal. He is a sensational talent."
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