The £26m January signing scored a brilliant solo goal in last week's 1-1 draw with Manchester United.
"Good player, good professional, good boy," Mourinho said ahead of the visit of West Ham on Tuesday. "Congratulations to my club, the way they did it.
"Initially – and I'm always very honest on this – he wasn't my first option when we decided to make a movement in the winter. But in the end, a great decision. A player with a great future, can play on the right and the left.
"We're more than happy, not just his age, but also his professional attitude. The way he trains, the way he lives. He's the kind of kid that can only be better."