Albion's under-23s suffered their first Premier League 2 defeat under interim head coaches Andrew Crofts and Shannon Ruth when they went down 3-1 to Manchester City on Friday.
The leaders scored twice from the penalty spot either side of Danny Cashman's smartly-taken equaliser at the American Express Elite Football Performance Centre.
The visitors carried the greater attacking threat but Albion stuck at it and Cashman nearly equalised late on before Liam Delap sealed his side's victory with a close-range goal in the last minute of stoppage time.
Moises Caicedo made his Albion debut and there was a start for Polish defender Michal Karbownik, but the hosts struggled early on as the leaders took a grip on proceedings.
The dangerous Felix Nmecha had already fired just wide when City took the lead from a 16th-minute penalty awarded when skipper Teddy Jenks brought down Romeo Lavia as he tried to clear his lines and Nmecha drilled the spot-kick into the bottom corner.
Gradually, though, Albion began to get into the game and they levelled in the 29th minute with a well-worked goal. Keeper Carl Rushworth started it when he found Caicecdo whose pass brought Karbownik into the attack. The Poland international's clever pass released Cashman and he took a touch before firing low into the opposite corner past Louie Mouldon.
Back came City and before the break striker Delap had two sights of goal, the first after a clever flick opened up space, but he failed to test Rushworth on either occasion.
The City no.9 did find the target four minutes after the break though when Jack Wakely was penalised for bringing down Delap in the box and Delap sent Rushworth the wrong way from City’s second spot-kick of the game.
Nmecha hit the post at the end of a City counter-attack but Lars Dendoncker wasn't away from equalising in the 62nd minute when his header from James Furlong's left-wing corner dropped the wrong side of the post.
Albion brought on strikers Evan Ferguson and Stefan Vukoje as well as Ayo Tanimowo and Cashman had a great chance with ten minutes left when he was put through on Mouldon's goal by Caicedo's long ball, but Mouldon saved with his outstretched left leg when Cashman tried to poke it past him.
City broke and substitute Cole Palmer's shot grazed the outside of the post before Nmecha squandered a great chance to make sure for his side but shot wide when it seemed easier to score.
Albion kept going but the visitors sealed victory on the counter-attack in stoppage time when Palmer set up Delap who beat Rushworth from close range.
Albion return to action on Sunday 7th March at Chelsea (2pm).
Albion: Rushworth, Karbownik, Dendoncker, Wakeley, Furlong (Tanimowo 77), Cashman, Weir, Caicedo, Jenks (Vukoje 87), Spong, Wilson (Ferguson 61).
Subs not used: Rees, Turns.
Booked: Caicedo