The Croats took advantage of a frail Ireland defence to win their opening match at the European Championship, getting two goals from Mario Mandzukic in a 3-1 victory Sunday night at rainy Municipal Stadium.
"I still can't believe what we just did. It was a fantastic victory," Mandzukic said. "We knew it would be a tough match, but we responded excellently and we achieved a great victory."
Croatia leads Group C with three points, while Spain and Italy each have one point after their 1-1 draw in Gdansk. Ireland, which is playing at a major tournament for the first time in 10 years, is last. The Croats next face Italy on Thursday.
"Probably one victory will be enough to go to the quarterfinals," Croatia coach Slaven Bilic said.
Croatia took the lead in the third minute when Mandzukic looped a header past a diving Shay Given, but Ireland equalized in the 19th when Sean St. Ledger headed in Aiden McGeady's free kick from the left.
Nikica Jelavic put Croatia back in front in the 43rd minute, scoring his first goal in a competitive match since he made his international debut in 2009.
"The second goal was clearly offside," Ireland coach Giovanni Trapattoni said.
Mandzukic added the third in the 48th after his header from Ivan Perisic's cross bounced off the post and into the net off Given's head.
Croatia nearly made it 4-1 in the 77th when Ivan Rakitic's shot curled just wide of Given's right hand post.
"Our coach showed us everything about the Irish team," Mandzukic said. "We had all the information."
The three goals were as many as Ireland had conceded in its previous 14 games.
"It was unlike us to concede the goals we conceded today," St. Ledger said. "Croatia didn't split us open. From our point of view they were disappointing goals to concede."
Bilic reinforced his defence by playing captain Darijo Srna at right back instead of midfield, and moving Vedran Corluka across to centre back.
"Since the first minute of the match, I was really sure and confident that we are the better team on the pitch," Bilic said.
There were no surprises from Trapattoni, an Italian veteran who had named his starting lineup days before the game.
"It's always nice to get goals, but we lost the game," St. Ledger said. "We need to move on now."
Ireland: Shay Given; John O'Shea, Richard Dunne, Sean St. Ledger, Stephen Ward; Damien Duff, Keith Andrews, Glenn Whelan, Aiden McGeady (Simon Cox, 54); Robbie Keane (Shane Long, 75), Kevin Doyle (Jon Walters, 53).
Croatia: Stipe Pletikosa; Darijo Srna, Vedran Corluka, Gordon Schildenfeld, Ivan Strinic; Ivan Rakitic (Tomislav Dujmovic, 92), Ognjen Vukojevic, Luka Modric, Ivan Perisic (Eduardo, 89); Nikica Jelavic (Niko Kranjcar, 72), Mario Mandzukic.