The brilliant Belgian still does not believe the Spain playmaker was allowed to join Manchester United for £37.1million in January.
Hazard said: "I was sad when Juan left because he was a good player. But at the end he was on the bench and he didn't play a lot.
"When you're a player, it's normal you want to play, so I respect his choice - but I wanted him to stay here because it was a pleasure to play with him.
"Playing with Mata was like playing with Cesc Fabregas. When you play with big players, you can learn a lot. Juan is my friend but I've not been in touch with him this season."
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