Smalling swapped shirts with Mata after England drew 1-1 with Spain in the European Under 21 Championship in June and believes he can improve a Chelsea side condemned as 'slow' by their own striker Fernando Torres.
Smalling said: "People are calling it a two-horse title race but Chelsea will be up there challenging. I know from playing against Mata that he's a great player.
"I think he will do well in the Premier League. He tends to roam and is difficult to mark. 'He has certainly made Chelsea more dynamic with his pace.
"He will definitely speed up the pace of their game."