Bramall Lane was the scene of the rare occurrence of a double sending off on Saturday as Barnsley and Sheffield United were reduced to 10 men.
Billy Sharp's 20th goal in his last 29 appearances had given the Blades an early lead as they went in search of a ninth consecutive home win.
But though the next 25 minutes passed without incident, three minutes before the break, what should have been a minor incident intensified in the South Yorkshire derby.
Racing onto a long ball forward from the Sheffield United backline, frontman Leon Clarke battled with Tykes skipper Angus MacDonald but the situation boiled over and became an off-the-ball incident in which Clarke seemed to grasp his opponent's neck.
A naturally incensed MacDonald squared up to Clarke, who in turn appealed to referee Tim Robinson. Following a discussion with his assistants, Robinson returned to brandish straight red cards for both men and leave both sides with ten.
The decision all-but curtailed hopes of a Barnsley comeback; they rarely threatened and fell to their third league defeat in four, while United climbed to tenth.