Michael O’Neill’s outfit drew 1-1 with Luxembourg in Belfast on Tuesday night following their 2-0 loss to Russia in Moscow on Friday and West Bromwich Albion skipper Brunt is not feeling confident regarding their qualification chances.
"We are disappointed we didn't see the game out and that's down to complacency," said Brunt.
"Luxembourg had confidence and worked hard but it was a pretty lucky goal towards the end of the second half and it went against the run of play.
"It will be an uphill battle now. We didn't do ourselves any harm against Russia, which was always going to be difficult, but now we have a mountain to climb in the next few qualifiers.
"We were dangerous from set plays and had chances, so it's easy to say it was one of those nights but we didn't take our chances."