Stoke City captain Ryan Shawcross was booked at halftime of their defeat at Manchester United.
Potters boss Mark Hughes revealed Shawcross was booked in the dressing room at halftime by referee Lee Mason.
Mason followed Shawcross up the tunnel to show him a yellow card and Hughes said: "Ryan was booked in the dressing room. The referee made a point of knocking on the door and booking him. I've no idea why.
"He pushed him (Van Persie) I think, but I've no idea because I didn't see the incident. But he wanted to book Ryan. I've never known anyone get booked in the dressing room before."
