The Dutch international joined the Red Devils when the former Ajax and Bayern Munich manager moved to the Premier League in 2014. The 20-time English champions won the FA Cup in Van Gaal's two-year reign at the club.
United parted ways with Van Gaal and replaced him with Jose Mourinho in the summer of 2016. Blind has struggled to feature regularly under the Portuguese tactician in the last two seasons at the club.
The 27-year-old,who started in 20 league games last term, so far has only three starts to his name this season. He has not featured in the Premier League since United's 1-0 win over Southampton in September.
Blind can operate as a centre-back, left-back and in the defensive midfield position. His compatriot believes the ex-Ajax captain's versatility will make him best suited for the Catalan club.
"Daley Blind is better off going to Barcelona, than staying with Man United. He is not even on the bench for United sometimes. Daley can play in more than one position and at Barcelona he would never be sat in the stand," Van Gaal told the Mirror.
"I think Daley would fit in better at Barcelona anyway. His level and his style of play is more suited to Spain than England.
"He can operate as a central defender who builds up the play. He can be a defensive midfielder or an attacking left back. Daley can do it all.''
According to Catalan publication Sport, Barcelona retain special interest in United's Blind. His contract runs down after the end of the season and has an option to extend it by a year. The La Liga giants could make an approach for his services in the January transfer window.
Mourinho has already stated that if a player is unhappy at United, he will be allowed to leave the club in January.
"I think for the right price. That's my approach as a manager. I think every player has a price," the former Real Madrid and Chelsea manager explained, as quoted by the Manchester Evening News.
"If a player is not happy, if a player brings with him the request with the number that we consider a good number for us - like with Memphis and Morgan - I would never say no."