The Colombian has a whopping 22 goals from 26 appearances so far this season.
Stubbs said on the Ladbrokes Social Club, "I think the biggest thing for me this season is that the fact that he is spending more time on the pitch.
"He is growing up as an individual. In the early part, he was a bit immature. I think he is got a big move [in him]. He is getting better and better each week.
"I think he is a top ten [sides in the Premier League] striker."