Van Wolfswinkel have shown stunning form, scoring nine goals in 11 appearances for Sporting Lisbon since joining the club from Utrecht in the summer.
The £11million-rated Dutchman is being tracked by a host of European giants.
Both scouts from United and Chelsea have watched the 22-year-old forward in action.
“I know they (Manchester United and Chelsea) are watching him but that is not unusual because they are watching all the best young players in Europe,” Louis Laros told the International Business Times.
“I have not spoken to anyone about his future. At the moment any interest is only rumours and nothing more.”
