Albion were beaten 2-1 by Blackburn Rovers at Ewood Park on Sunday afternoon.
Goals either side of half time from Ben Brereton Diaz and Sam Gallagher were enough to earn the hosts all three Sky Bet Championship points, despite Grady Diangana’s second period strike.
Steve Bruce’s men return to action this Wednesday when they host Cardiff City.
The boss named an unchanged team from Monday night’s last league encounter, opting to stick by the XI who put in an impressive performance against Watford.
And his side had the better of the opening 30 minutes, Darnell Furlong and Diangana both nodding dangerous Jed Wallace deliveries over and John Swift testing Rovers goalkeeper Thomas Kaminski via a dipping free-kick.
Yet, with their first effort at goal, it was Rovers who found a breakthrough before the interval - Brereton Diaz curling home from the edge of the box to send them into half-time ahead.
Blackburn’s Chilean international then turned from scorer to provider, his run and pass finding Gallagher to double their advantage immediately after the break.
But Albion found a way back into the contest just short of the hour mark – Diangana’s shot taking a deflection and wrong-footing Kaminski, giving the 2,000 travelling supporters hope that a comeback may be possible.
Bruce’s triple substitution, bringing on Okay Yokuslu, Matt Phillips and Callum Robinson, signalled his intent, however the hosts were holding firm by breaking up the game at every available opportunity.
Kaminski did well to deny Karlan Grant during a barrage of Baggies attacks, and Wallace volleyed over as the referee indicated 11 minutes of added time.
Though the visitors threw everything at Rovers that elusive goal equaliser wouldn’t come – consigning Albion to their first Championship defeat this season in Lancashire.
Albion: Button; Furlong (Phillips 61), Ajayi, O’Shea, Townsend; Molumby (Robinson 61), Livermore (Yokuslu 61); Wallace, Swift (Reach 90), Diangana, Grant.
Substitutes: Palmer, Bartley, Gardner-Hickman.