The veteran got on the scoresheet on Wednesday night in Manchester United’s 2-1 win over Fulham at Craven Cottage.
After a slow start to life at Manchester United, the 33-year-old has been coming into his own in recent games and has scored four times in 12 league appearances.
Cavani has already netted big goals for the Red Devils this season and Hargreaves feels Manchester United look a far more accomplished side with the Uruguayan leading the line for them.
He insisted that the other forwards are talented and will produce the goods Manchester United, but they cannot score the kind of goals the veteran striker will for the Red Devils.
Hargreaves, who is a big fan of Cavani’s off the ball movement, said on Premier League TV: “I love Cavani in the United team. I just think he gives them something so different.
“Marcus [Rashford] is really great, [Anthony] Martial has his moments where he can be great and Mason [Greenwood] is going to be a diamond.
“But Cavani, off the ball, his running is off the charts, he is flawless at it.
“He is going to get you goals that you think others probably [wouldn’t].
“You think of the Southampton goal, maybe the others possibly wouldn’t get. The kind of goals Ole Gunnar scored.
“That’s what United need.”
Cavani has made four starts in the league for Manchester United this season and is expected to play a bigger role in the second half of the campaign for the Red Devils.