Van Persie was a big influence on United's Premier League title triumph this season.
Smalling told manutd.com: "It's his overall approach and the way he goes about things. You can just tell he's top class. I remember when he first joined in training and everyone got a lift from that. He gets on really well with the lads which is really important because you have to all get on with the other players to make things work as a team. He's settled in straight away and he's shown how comfortable he is here by the way he is playing."