Both managers have appealed for calm

Violence marred Leeds' 2-1 Worthington Cup defeat in November, which sparked a pitch invasion from Blades fans.

But as the home supporters taunted Leeds fans they responded by ripping out seats and throwing them onto the pitch forcing mounted police to intervene.

It is one of a number of volatile incidents to have taken place at Bramall Lane this season, which has resulted in parts of the ground being closed for the match which kicks-off at 1130 GMT.

We don't want any problems from either side. It doesn't do the clubs any good and it doesn't do themselves any good Terry Venables

South Yorkshire Police have cancelled leave for the majority of their officers while the club have also drafted in extra stewards.

Venables said: "Obviously, this is a massive game for both clubs with plenty at stake.

"The fans can scream and cheer as loud as they want as long as they stay sensible.

"We don't want any problems from either side. It doesn't do the clubs any good and it doesn't do themselves any good."

Warnock was dismayed such a high-profile cup tie was being overshadowed by a minority.

"We have been tarnished all season with this minority at a time when we've never had such good coverage," he said.