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.
Chelsea are also set to play Liverpool in the semi-finals of the Capital One Cup, while Watford loom in the FA Cup third round.
With Chelsea threatening to dominate on all fronts, Hargreaves - winner of the Premier League and Champions League during his injury-plagued spell at Old Trafford - believes the Londoners are on par with the legendary United side that won the league title, the Champions League and FA Cup 15 years ago.
"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."
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