Ryan Mason believes conceding an equaliser so soon after taking the lead helped change the "feeling" of Wednesday night's encounter at Watford.
The Baggies were first to score at Vicarage Road - Isaac Price curling in a beauty from the edge of the box in the 34th minute.
However, the Hornets struck back less than four minutes later when captain Imran Louza fired home from a similar position to Price at the other end of the pitch.
Watford won it in the second period courtesy of Rocco Vata's close-range finish and the boss says the result was an extremely disappointing one.
Ryan said: “It’s always tough when you come away from home in this league, but the disappointing thing is that we got ourselves in a really good position in the first half and we let it slip.
“It was really important to get through to half time still in the lead, and we weren’t able to do that.
“In the second half, they’ve probably scored the winner in their best moment of the game. They came out and they had a spell at the start of the second half in the first 20 minutes where we had to try and get through it and understand the moment. It was obviously a key moment in the game.
“It didn’t help us with Alfie Gilchrist coming off and there was a quick turnaround from that moment to their winning goal.
“We tried to find an equaliser and the lads kept pushing. Isaac Price’s header is probably the best opportunity of the night for either team and their keeper has pulled off a really good save.
“We understand those moments are important and they can change the game with the momentum and feeling.
“It’s a really disappointing result, especially after we got ourselves in a really good position. I don’t know if our performance was enough to win the game, but goals change games.
“The nature in which we conceded the first was disappointing and that changes the feeling and then, as I say, understanding the moment of the second half in those first 15 to 20 minutes and trying to get through that because they were on top and they were having a positive spell is important. It was disappointing not being able to get through that.
“There was a bit of misfortune for the second and a ricochet in the box and then they’ve finished off the chance. We’ve got to understand why that’s happened and learn from it.
“The lads are disappointed because we don’t want to lose games and we don’t want to accept it. We don’t want to think that’s okay. We came here with the intention to win.
“It’s a disappointing night, but we have to recover quickly because we’ve got a game in just over 50 hours from now.”
