Northern Ireland boss Nigel Worthington has admitted that it was "horrible" to see his side gift Serbia a win at Windsor Park last night.
Glasgow Rangers midfielder Steven Davis' back-pass was intercepted by Olympiacos forward Marko Pantelic, who put the visitors ahead just after the hour.
The loss leaves Northern Ireland in fifth place in Group C ahead of their trip to Estonia on Tuesday.
"It's obviously a little knock," Worthington told Sky Sports News. "It's a blow. It's disappointing the way we lost the game.
"We expected Serbia to have a lot of possession, which they did, but second half we came out and probably over the course of the game, we were maybe the better side in the second half.
"But it's a horrible way to lose a game, it's unfortunate it happened but you deal with it and move on, simple as that. It can happen to anybody and unfortunately from Steve's point of view, it's happened to him."
Northern Ireland's next opponent, Estonia, defeated Slovenia away from home yesterday.
