Nigel Worthington was left angry and frustrated as Northern Ireland slumped to defeat in their opening World Cup qualifier.
Goals from Martin Skrtel and Marek Hamsik in the 46th and 70th minutes propelled Slovakia to a narrow 2-1 victory in Bratislava.
Jan Durica handed the province a lifeline in the 81st minute by diverting a cross from substitute Chris Brunt into his own net.
However, despite a frantic finale Northern Ireland failed to get the equaliser and Worthington could not hide his disappointment afterwards.
"It is a game we should have got something from,'' said the Northern Ireland boss.
"But through ill-discipline on set plays we have paid a heavy price and lost the game. That is the frustrating thing.
"In the first half Slovakia had a lot of possession but did not really hurt us. Then we go a goal down straight after half-time. That put us on the back foot as we never really got started in the second half.
"We [had] just got going again and they scored another goal. That meant we were really chasing the game.
"If we don't concede the second goal we go away with a point which is a fair result and gets you off the mark.
"In the last 15 to 20 minutes we showed more what we are about but the overall feeling is one of frustration -- but we just have to get on with it.''
Worthington is now hoping his side can bounce back at Windsor Park on Wednesday when they face the highly-fancied Czech Republic.
But the former Norwich boss is aware they can be formidable opponents. "It was a tough game before the Slovakia match and it is even tougher now," he said.
"But we are at home and the crowd will be there. We have got to put on a performance and get a good result.''
Keith Gillespie, who has been troubled by an ankle injury, could be doubtful for the match in Belfast.
The Sheffield United winger came off in the second half and Worthington added: "He got a heavy knock. We will monitor him in the next 24 hours, see what he is like and go from there.''
Meanwhile, new Slovakia coach Vladimir Weiss praised his side for their second-half display. "It was an excellent performance -- we played from the heart and gave 100 per cent," he said.
"I knew at half-time we had to change things and we pushed more men forward. We showed great spirit to win the match.''