Ankergren was apparently attacked during a minor pitch invasion following Millwall's goal in their 1-0 first-leg semi-final win.

Police horses were used to calm scenes at the ground, in south London, after a clutch of home supporters poured on to the pitch when Neil Harris scored his 117th goal for the Lions after 71 minutes.

A Scotland Yard spokesman said: "One man was arrested on suspicion of assault."

Leeds manager Simon Grayson played down the incident.

He said: "You know that in play-off semi-finals the atmosphere is quite hostile and people get exuberant.

"I thought the authorities handled it well, our players didn't respond to anything. I'm just here to protect my players, they're all okay and nothing much was made of it.

"Casper hasn't mentioned it. I wouldn't want to take Casper on if I was a Millwall fan anyway."