Danny Philliskirk netted a late winner as United's U21s edged out Premiership Wigan Athletic to begin 2013 with a win.
The Blades arguably shaded a closely fought encounter, but having moments earlier missed a good opportunity, Philliskirk acrobatically scissor kicked home from the resulting corner.
After a quiet opening to the contest, Ironside teed up Tonne for the first shot on goal, but his effort was inadvertently blocked by Philliskirk. At the other end the Latics came within a whisker of taking the lead when a deflected effort from Orsula narrowly went wide with Willis scrambling across his goal.
United pressed forward again and Ironside, who was heavily involved throughout, had two more sights of goal, although both efforts were easily saved by Marosi.
As half-time approached Wigan looked threatening from the flanks, although despite a number of crosses into the Blades penalty area, Willis was rarely troubled.
At the beginning of the second period, the visitors missed a wonderful opportunity to seize the initiative when Andres failed to beat Willis when clean through on goal.
With the clock ticking down United looked the most likely to nick a winner, Marosi produced a fine reflex save to deny Philliskirk, before Tonne fired over from a free-kick.
In the 88th minute, the hosts made their pressure count, having being denied moments earlier, PHILLISKIRK atoned by acrobatically firing the ball goalwards, giving Marosi no chance.
Deep into injury time Willis had to be at his best, producing an excellent save to ensure Chris Morgan's youngsters started 2013 with a hard fought success.
Blades: Willis, Westlake, McFadzean, Pemberton, Kennedy, Barry, Khan, Whitehouse, Ironside, Philliskirk, Tonne.
Unused: Smith, Lynch, J. Williams, Hodder, McDonagh.