Bruno Martins Indi will be pursued by both Ronald Koeman and Louis van Gaal, according to the Daily Mail.
The Holland international sparked fresh transfer gossip when he was quoted as saying, "Spiritually I still have contact with Van Gaal," before adding "I think about him and I think he also thinks about me".
Southampton are also credited with an interest in the Porto defender which could see the two Dutch managers fighting it out to sign the highly rated 22-year-old defender of the same nationality.
The Dutch defender signed for Porto after impressing at the World Cup but could complete a January move if Southampton or Manchester United provide the Portuguese club with an attractive offer.
The centre-back, who can also play at right back or as a holding midfielder, joined Porto from Feyenoord in July 2014 for a £6 million.