The Porto defender worked with Van Gaal in the Dutch squad at the World Cup last summer.
And according to reports, he’s keen on reunion at Old Trafford this winter.
United sent scouts to watch Martins Indi in action for his club against Chelsea in the Champions League a fortnight ago.
European heavyweights Bayern Munich, Barcelona, Roma and AC Milan are also said to be tracking the player, but Van Gaal is determined to bag the defender.
His value is reportedly around £19m which is unlikely to deter United from firming up their interest – particularly with Marcos Rojo seemingly heading for the exit after a bust-up with his manager.
Van Gaal is keen on bringing in a versatile left-footed player he can trust with youngster Luke Shaw likely to be on the sidelines until the end of the season with a broken leg.
The Dutchman has Ashley Young in place to play as a temporary full-back, but he’s not seen a long-term option for the role as Shaw continues his recovery.