The Leeds manager Terry Venables and his Sheffield United counterpart Neil Warnock are pleading for calm from both sets of supporters before tomorrow's potentially explosive FA Cup quarter-final showdown at Bramall Lane.
Violence marred Leeds' Worthington Cup third-round defeat in November, when injury-time goals secured a 2-1 win and sparked a celebratory pitch invasion from Blades fans.
However, triumph turned to trouble as the home supporters taunted Leeds fans, who responded by ripping out seats and throwing them on to the pitch, forcing mounted police to intervene.
That was one of a number of volatile incidents at Bramall Lane this season, which has resulted in parts of the ground being closed for the re-match.
South Yorkshire police have cancelled leave for the majority of their officers and extra stewards have been drafted in by the club.
Venables said: "It's a derby, which means it will be fierce and everybody wants to win. The fans can scream and cheer as loud as they want, but as long as they stay sensible."
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