Giggs won 34 trophies during his illustrious United career, including 13 Premier League titles and two Champions League crowns, as they established themselves as the dominant force in English football under Sir Alex Ferguson.
However, the Red Devils have not won the league title since Ferguson's retirement in 2013 and went through a trophiless 2017-18 campaign with Jose Mourinho at the helm.
"I think it always helps when you have the nucleus of players who know what the club is about or have been through the youth team. If you can get that then it is something very special. It doesn't happen very often, for that reason it is very rare," Giggs, who is now in charge of Wales, told ESPN.
"There was a really tight-knit group, not only the one's who had known each other for a really long time but we had Roy Keane, Ole Gunnar Solskjaer who were a similar age and we had a really good team spirit.
"I think it is always important to have that, it doesn't guarantee you success and if you don't have that it doesn't mean you aren't going to win."