Alan Irvine bemoaned defensive errors after watching his first defeat as Albion head coach.
It took Swansea only 88 seconds to open the scoring after Nathan Dyer capitalised on Jonas Olsson’s slip.
Wayne Routledge doubled the Swans’ advantage in the 24th minute before Dyer netted his second goal of the game after the break in the 71st minute.
Irivne admitted Albion’s plans were thrown out of the window in the second minute after the early goal.
“It couldn’t have been a worst start,” he said.
“Psychologically it’s difficult to react in the right way to that kind of start.
“You spend a week trying to get ready for the game, develop a game plan - and then somebody slips.
“That can’t be legislated for.
“We spent the time in the dressing room prior to the game talking about how important a good start was – and we got the worst possible start.
“It gave Swansea a boost and makes what would have been a tough game an even tougher one.
“We were certainly rocked by that and gave the ball away too cheaply, especially in the final third.
“When things were looking like they might settle down we made another mistake.
“Before you know it you’re 2-0 down and you’re standing on the side desperate for half-time to come because we needed to get in, regroup and help the players mentally, and make some adjustments.
“Full marks to the players because they responded well to that half-time break and made fewer unforced errors, kept the ball better and created some chances.”
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