Experience told as an under-strength United Reserves side were undone by a strong Hull City side on Tuesday evening, but there were plenty of positives for Ole Gunnar Solskjaer's side.
Goals from Dean Windass and Ryan France did the damage to United, but it was Greek international Stelios who called the tune, laying on both goals with subtle assists.
A late strike from Cameron Stewart and the performances of some of United's youngsters provided cause for consolation, however, with substitute Davide Petrucci particularly eye-catching on his Reserves debut.
With Richard Eckersley injured, and Danny Welbeck, Ben Amos, Danny Drinkwater and David Gray on international duty, Solskjaer called upon several members of the Reds' U18s to bolster his squad.
Winger Stewart deputised at right-back, Scott Wootton made his first start in the centre of defence and Jimmy Derbyshire occupied the left-back berth, giving the backline a much-changed look.
The presence of journeyman striker Windass - older than the Reds' two centre-backs put together - in Hull's starting line-up ensured a stern test for United and, although they withstood long periods of first-half pressure from the hosts, only six minutes of the second half had elapsed when Hull moved ahead.
Windass looped home a header from Stelios' chipped pass, but United's response was a positive one, and only a superb save from goalkeeper Matt Duke prevented Kiko Macheda from sidefooting the Reds level within two minutes.
Solskjaer's side mounted a spell of concerted pressure, before Hull extended their lead after 65 minutes. An inch-perfect one-two between France and Stelios ended with the former sidefooting home a neat volley.
Sam Hewson scuffed his shot when handed a decent sight of goal shortly afterwards, while substitute Evandro Brandao saw an effort cleared off the line in the last ten minutes.
Petrucci, who showed great awareness and pluck during his 20-minute cameo, then had a thunderous volley blocked by Duke as the Reds continued to press, and the visitors pulled a goal back in the third minute of injury time through Stewart.
The pacy youngster cut infield and caught everyone by surprise with a low 25-yarder which sneaked inside Duke's post. Too little, too late in terms of this match, but still plenty of positives from another valuable lesson for United's youngsters.
United: Zieler; Stewart, Wootton, Chester, Derbyshire; Eikrem (James 66), Possebon (Brandao 78), Hewson, Cleverley, Bryan (Petrucci 70); Macheda.
Subs not used: Johnstone, Strickland.