Mario Mandzukic gave Croatia the lead in the third minute but Sean St Ledger restored parity in the 19th minute as the Irish recovered from a shaky start.
However, Nikica Jelavic’s dinked finish put Slaven Bilic’s side in front with half-time approaching.
And any hope of an Irish comeback was extinguished two minutes after the break, when Mandzukic’s shot rebounded off the post and then Shay Given’s head to seal three points for Croatia.
Ward felt the Irish were unlucky as they stumbled to defeat ahead of daunting clashes with defending champions Spain and 2006 World Cup winners Italy.
“I’m devastated as we played really well in the game but the bit of luck we deserved definitely deserted us,” said Ward. “It was a tough game as they’re a tough side.
“It was an uphill battle [in the second half] but they didn’t play us off the park as the two teams were fairly evenly matched. The third goal straight after the break was a great header but it was a bit fortunate going in off Shay [Given].
“The travelling support was amazing and the lads gave it absolutely everything.
“[Against Spain] we have nothing to lose so we have to go out and give it everything and hopefully we can get a bit of luck on Thursday and then go into the Italy game with a chance of qualifying.”
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