Chelsea legend Ruud Gullit is impressed by the impact of Ricky van Wolfswinkel at Sporting Lisbon.

The former FC Utrecht striker is a confirmed target for Manchester United.

"The best sign about this player is that he's made a big jump going to Sporting and is still scoring goals," said Gullit. "He's proving a killer in the penalty area.

"It's not always easy for a Dutchman to succeed in a foreign league which has very different characteristics to what he's used to. I am delighted and proud that a fellow Dutchman is doing so well, especially at a club like Sporting."