Sam Johnstone admitted Albion "weren’t at their best" at Barnsley on Boxing Day.
The Baggies stopper made a string of impressive saves throughout the encounter, before finally being beaten by Aapo Halme in the 90th minute as the league leaders were held to a 1-1 draw at Oakwell.
And the No.1 says conceding so late on in the game has “hurt” the players.
Sam said: “We weren’t ourselves today, for whatever reason.
“You know that when you come to Barnsley it’s going to be extremely tough, especially given the run they have been on recently.
“They were fighting for every ball and we knew that’s the kind of test we would be facing today.
“It’s massively frustrating. It hurts even more when we know weren’t at our best and everyone is gutted that they have scored in the last minute.
“If we had come away with three points we probably would have thought that we had got away with one.
“But that’s football and we have to try and put it right against Middlesbrough on Sunday afternoon at The Hawthorns.”