Michael O’Neill admitted the nature of Bulgaria’s winning goal made Northern Ireland’s 1-0 defeat in Plovdiv on Sunday all the more frustrating.

On a poor pitch which affected both teams, Northern Ireland had survived an early onslaught in which Ciaron Brown blocked an early shot on the line amid a goalmouth scramble and Radoslav Kirilov hit a post with a fine free-kick.

Then, five minutes before half-time, Bulgaria’s goal came gift-wrapped as Bailey Peacock-Farrell’s mistake in trying to hit a short, square pass to Daniel Ballard rather than clear his lines allowed Aleksandar Kolev to set up an easy finish for home captain Kiril Despodov.

“It’s very disappointing,” O’Neill said.

“We knew it would be a tough game against a team we know have a lot of physicality, a lot of power in their team, and that was a factor in the early part of the game.

“I thought we dealt with that well but the nature of the pitch meant it was always going to be a game with more physicality in it than normal and ultimately we lost the game to a poor goal and that’s the most disappointing thing.”

Bulgaria, draw specialists who began the night with only one win in 16, were just about worthy of their victory given the pressure they had applied early on, but Northern Ireland appeared to have come through the worst of it only to undo their hard work.

The pitch had begun cutting up almost as soon as the game started, hampering the flow of the match.

Under those conditions, Peacock-Farrell was in a difficult spot when Brown played the ball back to him but had a chance to kick it long rather than look to square.

“The pitch is the pitch,” O’Neill added. “We knew about it going in and we talked about making good decisions in our own half.

“I haven’t seen the goal back in any detail but Bailey knows himself it was the wrong decision and ultimately that was the deciding factor in the game.”

O’Neill responded to the setback by shifting Conor Bradley to a more central position, which afforded Northern Ireland more of the ball in the second half.

But where before the break they had been able to create chances on the counter, now Bulgaria moved back and closed the door, with Northern Ireland rarely threatening in the second half despite a late push forward.

“We can’t control what the opposition do, they had something to defend which we gave them,” O’Neill added.

“I think they were more than happy to play on the counter (in the second half). The responsibility lies with us. The opportunities to counter weren’t there, so we have to improvise.

“I think for a lot of our players, they’re learning all the time, they’re learning at a good level.

“Tonight was a tough test, a difficult place to come and the second game in three days so as much as I’m disappointed to lose the game, there’s a lot to take from the game.”