Derby coach Wayne Rooney has condemned the behaviour of Millwall fans as "disgraceful and mindless" after they jeered players for showing support to the Black Lives Matter movement before kick-off on Saturday.
The Millwall and Derby players knelt before the start of the game in a gesture of support for the campaign against police brutality towards black people.
Millwall criticised the supporters' behaviour and pledged to prevent a repeat of the incident in subsequent home matches.
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Interim Derby manager Rooney expressed his "surprise" in an interview after the game, but has followed up with a stronger message denouncing of those responsible.