The Portuguese club reportedly made a £3million offer for the 18-year-old which appears to have been accepted by the Scottish Premiership side.
Gauld is now set to undergo a medical with Sporting, although it has not been confirmed whether or not he has agreed personal terms.
Scotland U21 international Gauld was a first-team regular for United last season and was rewarded with a new deal in December.
His impressive displays earned him the nickname ‘Mini Messi’ and saw him linked with European giants Real Madrid and Roma, while Manchester United and Arsenal are also thought to have taken an interest in him.
But Sporting could have won the race to sign Gauld, who returned to Tannadice for pre-season training on Monday.
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