Albion suffered a 2-1 defeat at Watford in the Sky Bet Championship on Wednesday evening.
Isaac Price netted an opener for the Baggies, however Hornets duo Imran Louza and Rocco Vata struck to earn Javi Gracia’s side all three points.
Following a quiet start, the game kicked into life around the half-hour mark when the visitors went ahead.
In-form Price - who also netted on the weekend - excellently curled home his fifth goal this season following a superb move involving Aune Heggebø and Mikey Johnston.
But the Baggies were pegged back seven minutes before the break through Louza’s attempt, with the Hornets captain finding the top corner from just outside the area.
And they went close to a second twice after the break as Luca Kjerrumgaard flicked a header narrowly wide and Souza dipped one onto the roof of Josh Griffiths’ net.
Watford’s pressure did soon pay off, though, as Vata converted a low 58th-minute effort to complete the turnaround and make it 2-1.
Still, Albion pushed forward again and could have equalised immediately via Price - the Northern Irish international seeing his close-range header somehow saved by Hornets goalkeeper Egil Selvik.
Griffiths had to keep out Tom Ince’s shot down the other end, while Jeremy Ngakia and James Abankwah threatened too.
Ryan Mason introduced Josh Maja, Karlan Grant and Daryl Dike to try and force an equaliser, yet they were unable to score, leaving Hertfordshire without any points.
Albion: Griffiths, Gilchrist (Campbell 55), Phillips, Mepham, Styles (Taylor 80), Diakite (Dike 80), Mowatt, Johnston, Price, Iling-Junior (Grant 70), Heggebø (Maja 70).
Substitutes: Wildsmith, Wallis, Deeming, Bostock.