The Chelsea loanee has reached the Champions League final with Borussia Dortmund. He spent last season on-loan at Turf Moor.
Kompany said: "It's an achievement for him and his parents, the people who have supported him to get to this level.
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"He's a kid who came in with a terrific attitude, he was in the Championship, he was a talented player but he was never too big for us in his mentality. He was willing to learn, talented at the start.
"I'm not surprised he's reaching those levels and I think we have players in this team that will go on to do the same."