(CNN) -- Spain's defence of their European Championship crown got off to an uncertain start as Vicente del Bosque's side had to come from behind in a 1-1 draw with Italy.
The World Cup holders lost their opening game in South Africa two years ago against Switzerland and when Antonio di Natale gave Italy a second-half lead another upset threatened.
Cesc Fabregas quickly equalised but Sunday's game in Gdansk provided evidence that the winners of Euro 2008 have work to do if they are to become the first team to win three successive major international tournaments.
Spain next face Republic of Ireland on Thursday, and the Irish lie bottom of Group C after a 3-1 defeat at the hands of an impressive Croatia in Poznan.
Striker Mario Mandzukic scored twice with headers, either side of a Nikica Jelavic goal for Croatia, and Slaven Bilic's side now lead the group with Ireland facing an uphill battle to qualify for the quarter-finals.
Spain 1-1 Italy
Spain coach Del Bosque chose not to play a recognised forward preferring to pack his team with creative midfielders -- much like Barcelona -- with the likes of Andres Iniesta, David Silva and Fabreas breaking quickly from midfield.
If this formation allowed Spain plenty of possession it was also a tactical set-up that was relatively vwell contained by Italy's organisation.
Iniesta tested Gianluigi Buffon with an early shot and later in the first half went close as he tried to lob the Italian goalkeeper, while Leonardo Bonucci well timed tackle prevented Fabregas from testing Buffon.
Not that Italy were solely content to sit back and soak up Spain's attacks - far from it -- and Iker Casillas was probably the busier of the two goalkeepers.
In the opening half the Real Madrid goalkeeper stopped two shots from Antonio Cassano, as well as an Andrea Pirlo free-kick, though the pick of the Spanish keepers's saves came just before the interval when he reacted quickly to push away Thiago Motta's goalbound header.
Early in the second half Mario Balotelli should have given Italy the lead following a mistake by Sergio Ramos but the Manchester City striker dawdled allowing the Spanish defender to retrieve the ball.
Almost immediately Italy coach Cesare Prandelli withdrew Balotelli, replacing him with Di Natale.
Within three minutes the switch produced immediate results as Pirlo sent Di Natale clear with the Udinese forward curling the ball past Casillas.
Italy's goal provoked an equally swift response from the defending champions as David Silva's flick flummoxed the Italian defence allowing Fabregas to sweep the ball past Buffon.
Finally Del Bosque decided it was time to bring on a foward, introducing Fernando Torres, who probably should have done better when he was sent clear by Jesus Navas' pass.
Soon afterwards Torres was sent clear for a second time but his attempted lob went over the bar.
Croatia 3-1 Republic of Ireland
Sunday's second Group C contest was supposed to take second billing, but in torrential rain in Poznan the Croatians laid down a marker for the tournament with a clinical display against the Republic of Ireland.
It had been 10 years since the Irish last qualified for a major tournament and their noisy fans seemed keen to make up for lost time, but with less than three minutes gone they were silenced by a Croatia goal.
Ireland's marking went missing as Mandzukic was given all the time in the world to head Darijo Srna's deflected right-wing cross into the net, with Irish keeper Shay Given struggling to get across his line.
The goal temporarily stunned Ireland but they always carried a threat from set-pieces which eventually brought them an equaliser.
Aiden McGeady's wickedly inswinging free-kick from the left caught Vedran Corluka cold at the back post, as Sean St Ledger sneaked in to head past Croatia keeper Stipe Pletikosa.
It was the Croatians' turn to look rattled but the game was opening up beautifully as both teams saw the value in going for victory and three vital points with matches against holders Spain and Italy still to come.
Croatia coach Bilic leaves his post after the tournament after a successful six-year spell in charge and three minutes before half-time, he saw his team take a lead that this time they would not relinquish.
More sloppy Ireland defending led to Stephen Ward slicing a clearance straight into the path of Jelavic, and as he showed last season at Everton, the striker is a deadly finisher inside the penalty area as he clipped calmly over Given.
Soon after half-time it was all over as a lightning-quick Croatia break led to Mandzukic's header coming back off the post, hitting Given on the back of his head and -- unfortunately for the Ireland goalkeeper -- rolling into the net, though the Wolfsburg forward was given the goal.
Ireland tried hard to find a way back into the match and Robbie Keane had an appeal for a penalty turned down, but Croatia were too strong and held on with ease to move top of Group C ahead of a meeting with Italy in Poznan on Thursday.