Everton defeated the Championship side 2-1 on Tuesday evening to advance in the knockout competition, but the result was somewhat marred by an injury to Stones.
The centre-back was replaced early in the second half, clearly in some discomfort, but the Spanish manager has moved to insist that the defender is not set for a long spell on the sidelines.
“John was withdrawn as a precaution more than anything. He had a knock in his knee and we couldn’t take any risks,” Martinez began.
“He will be assessed over the next 48 hours but I don’t think it’s serious.”
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The Spanish coach’s comments will come as a boost to Toffees fans, as Stones should be a safe bet to return for the upcoming Merseyside derby against Liverpool in two weeks.
Against Reading, Everton fell behind to Nick Blackman’s opener, although Ross Barkley bagged an equaliser just after the hour mark.
Loanee Gerard Deulofeu settled the tied with a magnificent free kick late on.