The substitute defender was the hero of the hour (and a half) when he headed home deep into stoppage time to send the Blades into the second round of the League Cup, and by the time Morecambe had made their way back to the centre circle there was all but a minute remaining.
Blades boss Nigel Adkins made seven changes from the side whilst lost 4-0 at Gillingham last Saturday. David Edgar was given his debut having joined on a season's long loan from Birmingham City just 24 hours previous and Mark Howard was given a stint in goal with Conor Sammon partnering Marc McNulty in attack.
A first ever visit to Morecambe's Globe Arena saw the Blades get off to a bright start with the first opportunity on the night falling to McNulty five minutes in but he was unable to comnnect after James Wallace and Freeman combined. At the other end Howard was tested by Beeley and Freeman was called into action, preventing Molyneux and Wilding from capitalising.
Little happened in terms of further opportunities for either side but as the first half was drawing to a close the hosts came with two chances of their own. Firstly Devitt fired and his shot appeared to swerve in the air but Howard was able to make a reaction save and in a crowded penalty area Edwards saw his effort blocked.
At the break Adams was introduced for Woolford and the highly rated youngster caused problems for the League Two defence, he was quickly in with a chance from the start but the keeper was able to save with his legs following Scougall's ball through.
This one move encouraged the Blades to attack and within the next ten minutes to follow Sammon headed goal wards from McNulty's cross but the on loan Derby man's effort was deflected wide, Scougall then produced a cross which was headed wide by Edgar and Adams teed up Freeman before the full-back fired over the top.
Sammon was gifted with another opportunity on the hour mark, after Scougall had robbed Fleming the striker hit his shot wide of the goal. Morecambe was handed their first chance of the half as Parrish headed over from a corner. With ten minutes remaining, looking to get back into the game the hosts made a substitution as Molyneux was replaced by former Blade Shaun Miller.
Mullin was next to go close but the former Rotherham striker hit the side netting. United were soon on the offensive and Edgar saw another header kept out, Roche saved again with his legs from Adams and McNulty fired a deflected shot wide as chances rained Morecambe's goal.
With extra-time and at this rate penalties looming the hosts made a breakaway and Devitt was on the attack, but almost in the opposition box he made the wrong decision and was crowded out. Before the referee was ready to blow up for full-time there was just one more chance on goal left and United took it. James Wallace provided a corner from the left and substitute COLLINS rose highest to land a powerful header past Roche and into the old onion bag.
Morecambe: Roche, Beeley, Edwards, Devitt, Molyneux (Miller 80), Mullin, Goodall, Wildig (Kenyon 57), Fleming (Ellison 71), Wilson, Parrish. Unused: McGowan, Thompson, Ryan, Doyle.
Sheffield United: Howard, Freeman, J Wallace (Reed 90), Basham, McNulty, Scougall, Woolford (Adams 45), Sammon, McEveley, K Wallace, Edgar (Collins 84). Unused: Sharp, Collins, Higdon, Long, McFadzean.