Croatia made a flying start to Euro 2012 after pouncing on sloppy defending to beat Ireland 3-1 in their Group C opener on Sunday.
Ireland, whose 14-match unbeaten run came to an end, could not have made a worse start to their first major tournament for 10 years as they allowed off-balance Mario Mandzukic too much space to head Croatia ahead after three minutes.
Sean St Ledger headed Ireland level after 19 minutes but Croatia regained the lead three minutes before the break when Nikica Jelavic was left alone to prod the ball past goalkeeper Shay Given with Ireland appealing in vain for offside.
A unlucky Given own goal at the start of the second half effectively ended Ireland's chances and put Croatia top of Group C after Spain and Italy drew 1-1 earlier in Gdansk.
"It was very important that we scored an early goal, they are really good fighters, it wasn't that easy," Mandzukovic said.
St Ledger rued the concession of sloppy goals.
"Unlike us," he said. "We are usually pretty tight. We knew in the second half we had to come out. The next goal was going to be important and they got it.
"When you are 3-1 down against a side like Croatia it is always going to be tough. They were poor goals to concede," St Ledger added.
Croatia could be in trouble after their fans celebrated their second goal by letting off firecrackers and flares.
Ireland's 73-year-old coach Giovanni Trapattoni had hoped to frustrate Croatia but that plan was blown apart with an odd early goal.
Mandzukic, who had stumbled from his knees and was unmarked, got up just in time to head Darijo Srna's cross from the right past a stranded Given.
However, Ireland regrouped well with Damian Duff hooking a shot wide and Keith Andrews wasting a great chance by firing into the wall after a free kick.
They leveled in the 19th minute when Aiden McGeady floated a long free kick over from the left and St Leger at the far post got ahead of Vedran Corluka to head the equalizer.
The game then became bogged down in midfield with technically-limited Ireland struggling to play the ball out of defense and Croatia also looking disjointed.
But, with playmaker Luka Modric coming to life, Croatian began to play more thoughtful football and looked more threatening.
Ivan Perisic had a powerful drive parried by Given and volleyed wide again from just outside the area before they regained the lead with more Irish help.
Modric's low pass hit two Irish defenders on its way through the defense and landed at the feet of in-form striker Jelavic who diverted it past Given.
Croatia started the second half in the same way they began the first, an excellent build-up ending with Perisic crossing the ball into the area.
Mandzukic met it with a header, the ball hit the post and ricocheted against the hapless Given and into the net.
Ireland fought on but the task looked too much for them and they must now beat at least one of Spain or Italy to have any chance of progressing.
(Editing by Justin Palmer)