The unnamed United star had to be given a lift to the airport by a police officer as he was struggling to provide a urine sample after United's 1-0 defeat.
Police in Rotterdam produced the following tweet.
Einde dienst. 1 speler van MU op het nippertje op het #vliegtuig gezet. Kon niet plassen bij de #dopingcontrolepic.twitter.com/6LCXMrsE0D
— RE_Klipsteen (@RE_Klipsteen) 15 September 2016
The message translates as: "End of service. One player from [Manchester United] narrowly put on the plane. He could not pee at doping control".