Chelsea are on track to claim a historic quadruple this season, with the London outfit firing on all cylinders.
Jose Mourinho's men are flying high in 2014-15, top of the Premier League table and into the UEFA Champions League round of 16 where they will face French champions Paris Saint-Germain.
"When I look at the Chelsea team it reminds me of how we were back in 1999," Hargreaves told The Mirror.
"Our team was perfect.
"We had great skill, great athleticism, great physical strength. And we were ruthless, in a good way. Looking at Mourinho's side I see the same qualities – especially the ruthlessness.
"Jose doesn't let players get away with anything but they respect and admire him for that.
"Louis van Gaal is also like that at Manchester United now. Too much accountability and being nice just doesn't cut it. Players will respond to tough bosses.
"Too much freedom and they take advantage."
