Manchester United defender Chris Smalling has hailed the impact of summer arrival Robin van Persie.

Van Persie took his tally at United to 15 goals in 21 games with the opener in Saturday's 3-1 home win over Sunderland.

"I saw the finish," said Smalling.

"It wasn't easy to put it in that top corner but he is a quality player. Obviously he only came in the summer and didn't have much of a pre-season.

"But he came straight into the matches and has been such a threat. He is putting teams on the back foot and making our job easier at the back."