ALBION could not find the breakthrough - despite creating a host of good chances - as they were undone 1-0 at Watford.
The Baggies, backed by a sell-out 2,200 following who travelled to Hertfordshire in superb voice despite the adverse weather conditions, played on the front foot and largely enjoyed the better of the encounter.
Salomon Rondon went close on more than one occasion at Vicarage Road, as did Grzegorz Krychowiak while captain Jonny Evans struck a post.
But the Hornets, who threatened themselves and saw Stefano Okaka's shot cleared off the line by Kieran Gibbs, provided the game's only goal when Troy Deeney was sent clean through to convert in the 77th minute.
Albion, who handed recalls to Chris Brunt and Jake Livermore, started brightly with Krychowiak seeing his goalbound strike blocked from 12 yards out.
Roberto Pereyra saw a similar chance shut out by Gibbs at the other end but it was largely the visitors who dominated the opening quarter.
Rondon headed just off target as the Baggies created a number of half-chances but, as the Hornets grew into the game, it was Ben Foster who came to the rescue to poke wide Daryl Janmaat's low effort with his foot.
Brunt curled a free-kick on to the roof of the net just before the break as the first half ended goalless.
Albion flew out of the blocks at the start of the second half, Rondon twice forcing saves from Hornets goalkeeper Orestis Karnezis in as many minutes.
Evans struck the base of the near post from a Brunt corner while Richarlison acrobatically hooked wide for the home side.
Rondon then headed a golden chance off target from just outside the six-yard box in the 54th minute.
A stretched encounter became end-to-end and Andre Carrillo sent a long-range strike narrowly over the crossbar.
Janmaat threw his body on the line to deny a diving Jay Rodriguez before Gibbs cleared off the line from substitute Okaka.
But it was Watford who claimed all three points as sub Will Hughes won the ball in the middle of the park and sent through Deeney, who finished calmly into the top corner.
ALBION: Foster, Dawson, Hegazi, Evans (c), Gibbs, Phillips, Krychowiak (McClean 81), Livermore (Field 87), Brunt, Rodriguez (Burke 87), Rondon.
Subs: Myhill, Nyom, McAuley, Yacob.