Bernt Haas celebrates his opening goal
West Brom 2-0 Man Utd
West Bromwich Albion handed out a harsh lesson to a young Manchester United side by putting them out of the Carling Cup.
Sir Alex Ferguson's enthusiasm to blood some of his young stars backfired as Albion's experience booked them a place in the quarter-finals of the competition at the expense of last season's finalists.
After a 15-minute delayed start, goals from Bernt Haas and Scott Dobie ensured Jason Koumas's penalty miss did not prove costly.
First Division leaders West Brom made a positive start and United's second-choice goalkeeper Roy Carroll was forced into an early acrobatic save to prevent Danny Pugh sending a firm header
into his own goal.
Carling Cup quarter final draw
Aston Villa v Chelsea
Tottenham v Boro
Bolton v Southampton
West Bromich Albion v Arsenal
Games played week of 15 Dec
But the Northern Ireland keeper had no chance the next time Albion pushed forward.
Neil Clement's left-wing cross was diverted into the path of Haas who,
from just inside the United box, sent a volley crashing into the corner of the net.
A nervous slip from John O'Shea nearly saw Danny Dichio play Rob Hulse in as the
fledgling United line-up struggled to handle their vastly more experienced
Ronaldo ballooned a 20-yard effort over not long after he had seen a free-kick fizz off Thomas Gaardsoe's head for a corner.
The First Division side had a great opportunity to double their lead on 24 minutes when Pugh upended Koumas in the penalty area.
6mins: Haas volleys Albion ahead.
24mins: Koumas penalty saved by Carroll
49mins: Dichio header comes back off the bar
56mins: Scott Dobie makes it 2-0
Welsh international Koumas picked himself up and placed his spot-kick low to Carroll's left but the Irishman plunged to save.
Koumas was an impressive figure in midfield and another surging run produced a cross for Dichio to plant an unmarked header straight at Carroll.
But United still carried a threat and David Bellion crossed for Nicky Butt, who placed his header close to Hoult, allowing him to save.
The Baggies took up the running at the start of the second half and Haas powered down the right to whip in a cross for Dichio, whose looping header beat Carroll and crashed back off the underside of the bar.
Roy Carroll saves Jason Koumas's penalty
Kleberson offered a reminder that United had a World Cup winner in their ranks
when he forced Hoult into his best save of the night with a fierce 20-yard
West Brom needed the cushion of a second goal and got it on 56 minutes with what boss Gary Megson will claim was an inspired substitution.
Scott Dobie was introduced for Rob Hulse and with his first touch of the ball headed Neil Clement's cross past Carroll.
Danny Pugh looked neat and tidy at left-back but Manchester United's inexperienced youngsters struggled to find a route back into the game.
West Brom: Hoult, Gregan, Gaardsoe, Gilchrist, Haas, Koumas, O'Connor, Johnson, Clement, Hulse, Dichio. Subs: Murphy, Dobie, Sakiri, J Chambers, A Chambers.
Manchester United: Carroll, Bardsley, O'Shea, Tierney, Pugh, Fletcher, Kleberson, Butt, Richardson, Ronaldo, Bellion. Subs: Williams, Eagles, Wood, Nardiello, Jones.
Referee: J Winter (Stockton-on-Tees).