Michael O’Neill was keen not to overstate the significance of defeat after his Northern Ireland players fell to a l-0 Nations League loss away to Bulgaria on Sunday.

Northern Ireland travelled to Plovdiv in buoyant mood after a run of four wins and only one loss – which came in a friendly away to Spain – in their last six.

But on a poor pitch and in front of a small but noisy crowd at the Hristo Botev Stadium, O’Neill’s men were undone by an avoidable defensive mix-up five minutes before half-time as Bailey Peacock-Farrell’s misplaced pass to Daniel Ballard was picked off by Aleksandar Kolev before Kiril Despodov swept home.

Northern Ireland, who won their League C3 opener at home to Luxembourg 2-0 on Thursday night, dropped to third in the standings behind both Belarus and Bulgaria – their opponents in the next two fixtures respectively in October.

For a seventh-straight game, O’Neill fielded a starting XI with an average age under 25. Having warned that it would not all be plain sailing with a young group, the manager stressed against reading too much into the result.

“It’s not a setback, it’s a defeat,” the manager said. “We’re a tiny country with a very limited group of players. I think the expectation has to be measured, the expectation that we would come here and win the game…

“We said to the players at the outset, ‘the aim is not to be beaten’. I think Bulgaria have turned a corner in the last six or seven games as well.

“Going forward we’re going to lose games. We just have to learn from that. I’m not really sure I’d call it a setback, a bump in the road, or refer to it as anything. We lost a game away from home.”

The pitch – which began cutting up almost immediately – made life difficult for both sides. O’Neill did not want to use it as an excuse, but was clear in his feelings about it, saying: “It’s not what you expect in international football.”

Northern Ireland came under pressure straight from the start.

Bulgaria will still be wondering how they did not score from a goalmouth scramble just three minutes in, with Peacock-Farrell pulling off a pair of saves before Ciaron Brown cleared off the line, and Radoslav Kirilov then hit a post with a free-kick.

After the goal, O’Neill changed the approach and Northern Ireland began to exert more control, although they actually created fewer chances in the game from that point on as Bulgaria dropped back to reduce the opportunities for counter-attacks.

“Just before half-time we changed Conor (Bradley) to play more in a midfield three and for Isaac (Price) to play closer to Dion (Charles), almost as a front two with split strikers,” O’Neill addedd.

“I felt it gave us a little bit more control but it was tough because they played with four against our back five and it made it difficult.

“But we did get control in the game in a lot of areas after that so it’s something for us to look at going forward and maybe a better way for us to think about starting the game – particularly away from home.”