Albion's six game unbeaten run came to an end as Wigan Athletic stalled the Baggies' promotion push with a well earned 1-0 victory at The Hawthorns.
The Baggies were well below par and struggled to create any meaningful chances against a well drilled and determined Wigan side.
Sam Morsy's second goal against the Baggies this season in the 73rd minute was enough to give the visitors a much needed victory in Latics' battle against relegation.
Slaven Bilic stuck with the same side that impressed against Preston in the week.
But Albion struggled to find any tempo and looked devoid of any creativity with Matheus Pereira and Callum Robinson well shackled.
Baggies keeper Sam Johnstone was the busier as he made a number of important saves to keep Albion in the game.
Wigan forward Gavin Massey hit a post with a close range header before the break as Albion failed to build on their recent good win.
The defeat, plus Leeds' win at Hull, means the Baggies are a point clear at the top of the Championship - and six ahead of third-placed Fulham.