Crawley extended their unbeaten run to six games after another memorable night at Bramall Lane.
Reds completely dominated the first half and were well worth their lead given to them by Jamie Proctor after nine minutes.
There was to be no repeat of their 2-0 victory at Sheffield United last season, however, as the home side came back strongly after the interval and grabbed an equaliser through Marlon King in the 63rd minute.
The result lifted Crawley to eighth place in League One while the Blades climb three places to 21st as they avoided a seventh straight league defeat.
Boss Richie Barker had said that a good start was vital to heap more pressure on United and turn the crowd against them.
He got exactly that as Reds took the lead after just nine minutes from a brilliantly worked corner routine. Andy Drury laid the ball in to Billy Clarke at the near post whose backheel was perfect for Drury to dink a chip to the far post which Proctor headed home.
It was no less than Crawley deserved for their positive play against a Blades side which looked horribly out of confidence following a run of six straight league defeats.
Reds should have had a second midway through the half when a superbly weighted ball from Drury put Mat Sadler away but he shot wastefully wide with two men queuing up at the far post.
The visitors continued to look the more threatening and they had another excellent chance to double their lead just before half-time. Joe Walsh surged out from the back to slide in Proctor but his shot crashed into the side-netting.
United’s performance in the first half was summed up in injury time when a tame shot from Fabien Brandy was greeted with loud sarcastic cheers from the disgruntled home fans.
The home side could only get better in the second half and so it proved. They were so nearly level after 53 minutes when Tony McMahon crashed a 25-yard shot against the inside of a post with Paul Jones well beaten.
It proved a warning as the equaliser arrived in the 63rd minute. Fabien Brandy slipped a clever ball through to King who slid his shot past the advancing Jones.
The goal lifted United and they looked the more likely to grab a winner. It nearly arrived with seven minutes to go when substitute Conor Coady pulled the trigger from 20 yards but Jones got down well to turn the ball around his near post.
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