The Frenchman is fully behind the Chelsea boss's decision to part with the playmaker saying the Spaniard was too weak for the Premier League and not as capable as Willian
Mata was a popular figure with Chelsea supporters during his near three-year stint at Stamford Bridge, but failed to nail down a regular first-team place under Jose Mourinho this season.
The 25-year-old duly completed a switch to reigning Premier League champions Manchester United in a £37.1million deal during the January transfer window.
While Mourinho's decision to part company with such an asset may have raised eyebrows among some supporters, Leboeuf - who spent five years with Chelsea - believes the Portuguese made the right decision due to the wealth of attacking talent at his disposal.
"I've never been a big fan of Juan Mata," Leboeuf told Perform. "I think he's a fantastic player (but) I think he doesn't suit English football.
"I guess Chelsea tried to find the new (Gianfranco) Zola. But Zola was much more powerful than Mata, and Mata is a little bit light.
"I think Mourinho realised that and that is why he bought Willian, because he has a little bit of Zola, not as big as Zola but strong, skilful and works really hard for the team and can defend.
"With (Eden) Hazard, Oscar and Willian, it is an armada. You don't know where to look, because you know you are going to struggle at some point."