The youngsters opened the door to their rivals in the race for the play-offs after a defeat in Manchester on Saturday morning.
Saints were pegged back in the Elite Group standings as United made up ground on them with a victory secured by two second half goals which pushed the Red Devils onto 20 points – the same as Saints – but with a game in hand on Jason Dodd’s side.
The visitors had difficult blustery conditions to deal with, but were able to create some early half chances with both Gboly Ariyibi and Sam Gallagher each going close in the opening exchanges, before the hosts took the lead on 18 minutes when a rebound from a shot saved by Chris Johns was put away.
Dodd’s side stayed in the contest until the break, but opportunities dried up in the second 45 as the visitors were undone again on 64 minutes when a bullet header from a cross on the left doubled United’s advantage.
It was 3-0 on 77 when a long range strike found the top corner, which consigned Saints to their third consecutive defeat, following on from setbacks against Bolton Wanderers and Fulham.
There are just two games remaining for the U18s who host Everton next weekend before travelling to Reading, in the hope that both Fulham and United will slip up in their remaining fixtures.
“We’re not getting up for the big games at the moment and that is a concern,” Dodd said post match.
“Maybe it’s a situation we can’t handle, but it’s something we need to address. Perhaps we need to get back to basics, because we’ve now lost three in a row and it’s a long time since we’ve done that.
“Today we struggled to create any quality. We played too many long balls, and didn’t get going despite starting the game quite well.
“We left Jake Flannigan and Charlie Higgins behind as they were ill, but I won’t use that as an excuse because we’re trying to look after everyone as we’ve got a big game now against Everton next week which will be another tough test for us, and we’ll have to give all we can.”
Saints U18s: Johns, Leggett, Mugabi, McCarthy, Colmer, Gape (Mason 80), Reed, Ariyibi (Sims 65), Rowe (Hesketh 60), Seager, Gallagher