United's U18s slipped to a late defeat against Birmingham City at Shirecliffe.
Substitute Jerome Slew equalised for the Blades after City had taken the lead through a free-kick, only for Ioan Evans to put through his own net under pressure with four minutes remaining.
A bright start by the Blades led to opportunities for both Calvert-Lewin and Cockerline, although Birmingham themselves had chances on the counter attack.
An even first period ended goalless, although United will have probably felt they edge the game and will have been slightly disappointed not to have gone in front.
The second-half followed a similar pattern, but it was the Blues that took the lead in the 55th minute, when a long-range free-kick squirmed under the wall and beyond the outstretched arm of Eastwood.
Birmingham then hit the woodwork in their next attack, before all three of the Blades substitutes had a hand in a well worked equaliser.
In the 75th minute, Gordon, Ramsey and SLEW all combined before the latter finished when clean through on goal. United then pressed for a winner and Calvert-Lewin should have scored after recovering a loose ball with the Birmingham goalkeeper out of position.
But it was the visitors that netted the decisive goal in the 86th minute, when Evans diverted a dangerous cross from the left into his own net, giving Eastwood no chance.
Blades: Eastwood, Sheron (Gordon 59), Kedman, Ishmail, Cheeseman, Evans, Heh, Brooks (Ramsey 64), Cockerline (Slew 69), Calvert-Lewin, Hinchliffe.
Unused: Adebowale, Ramsdale.