HOW DO THEY PLAY?
Guiding a squad that has won everything already, Vicente del Bosque has to cope with the prospect of key players that are "melted" (in the words of Zinedine Zidane) with tiredness after a punishing schedule. The coach did this superbly at World Cup 2010, playing a more containing than dynamic possession game, which almost became a 4-3-2-1. Sergio Ramos is likely to move to centre-back to replace the injured Carles Puyol, though Athletic Bilbao's Javi Martínez could help circulate the ball better.
Likely formation: 4-2-3-1
Possible starting XI: Iker Casillas; Alvaro Arbeloa, Sergio Ramos, Gerard Piqué, Jordi Alba; Sergio Busquets, Xabi Alonso; Xavi, Andrés Iniesta, David Silva; Fernando Llorente
Tricky. Spain has an incomparable galaxy of glittering talent. But, if there's one man they might - just might - miss, then you'd plump for pass-master Xavi (pictured right). The Barcelona midfielder is the world class linchpin around which his world class colleagues (for club and country) weave their magic, pinging his way out of trouble and carving delicious gaps that no other player on the planet can conjure. Minute upon minute. Match upon match. Season upon season. Xavi oozes dominant class.
He was Uefa's player of the tournament at Euro 2008, when he completed 89% of his passes, including an assist for Fernando Torres' winner against Germany in the final. He was just as influential at the World Cup - on average, he attempted a pass every 57 seconds in South Africa.
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With David Villa recovering from injury and Fernando Torres trying to rediscover his best form, Fernando Llorente will hope to get a chance up front. In outstanding form for the Athletic Bilbao side which reached both the Europa League and Copa del Rey finals this season, Llorente's displays have made him one of the most coveted strikers on the continent.
His strength and aerial ability give Spain a completely different attacking option, but the 27-year-old has shown at club level that is much more than a mere battering ram; his build-up play, first touch and finishing skills are also exceptional.ITALY
HOW DO THEY PLAY?
Italy have made a real effort to change style under Cesare Prandelli. Even though they booked their place at the Euros with the best defence in qualifying they're no longer a negative, counter-attacking side honouring the tradition of catenaccio. Instead the four-time World Cup winners look to impose themselves on the opposition with an attractive possession-oriented game based around a midfield of piedi buoni or good feet. Their aim is not just to win, but to convince too.
Likely formation: 4-3-1-2
Possible starting XI: Gigi Buffon; Christian Maggio, Andrea Barzagli, Giorgio Chiellini, Domenico Criscito; Claudio Marchisio, Andrea Pirlo, Daniele De Rossi; Antonio Cassano; Mario Balotelli, Antonio Di Natale.
Ignored by Marcello Lippi, temperamental forward Antonio Cassano (pictured right) has flourished under current Azzurri coach Cesare Prandelli.
Since joining AC Milan he has contributed more assists than goals, but he was prolific in qualifying, netting six times.
Cassano's dreams of playing in a third European Championship looked in doubt after he suffered a transient ischaemic attack - something often described as a "mini-stroke" - on the flight back from Milan's game away to Roma in October. He was barely able to speak or move, and admits he feared for his life.
A few days he later he underwent surgery to close a small opening in his heart. He was able return to light training in January, and made his first-team comeback in April.
After starting off with Bari, Cassano's spells with Roma, Real Madrid and Sampdoria all ended in acrimony, but Prandelli insists his enthusiasm is "contagious", adding "I need players like him".
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Mario Balotelli only played 19 minutes during qualifying, but the serious injury suffered by Giuseppe Rossi means the Azzurri are short of attacking options.
He scored his first international goal in November's win in Poland, but was dropped for the next squad as punishment for his indiscipline at club level. Prandelli called his behaviour "a sign of weakness", adding "you can't be in the national squad if you risk leaving the team with 10 men."REPUBLIC OF IRELAND
HOW DO THEY PLAY?
Former Ireland midfielder Matt Holland: "Ireland's success in qualifying has come from being difficult to beat. They have an outstanding goalkeeper in Shay Given, and Richard Dunne has been solid in the middle of the defence, while the full-backs tuck in and defensive midfielders remain disciplined.
"Creativity is down to the two wide men in Aiden McGeady and Damien Duff, who often switch wings, with forwards Robbie Keane and Kevin Doyle making a front four. An added extra is Sunderland winger James McClean, who has made an impact in the Premier League and gives Ireland a more direct option."
Likely formation: 4-4-1-1
Possible starting XI: Shay Given; John O'Shea, Richard Dunne, Sean St Ledger, Stephen Ward; Aiden McGeady, Glenn Whelan, Keith Andrews, Damien Duff; Robbie Keane; Kevin Doyle.
Robbie Keane (pictured right) was Ireland's top scorer at their last major tournament, the 2002 World Cup, and almost a decade later the Dubliner remains the chief Irish goal threat.
He contributed seven goals in qualifying, an impressive tally from a side that often struggles to create clear-cut chances. The captain may have lost a yard or two of pace, but there is no doubting the predatory instincts that have made him Ireland's record scorer with over 50 goals.
The 31-year-old joined Los Angeles Galaxy last August, and created the only goal in the MLS Cup final. The striker used the winter break to recharge his batteries in time for the 2012 season, also spending a brief but productive loan spell at Aston Villa. Fatigue should not be an issue for him this summer.
Keane scored three times in four appearances at the 2002 World Cup, with his injury-time goal in the 1-1 draw with Germany the highlight of the tournament for many Irish fans.
He was part of the Irish team that won the European Under-18 title in Cyprus in 1998, although he missed in the penalty shoot-out win against Germany in the final.
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In an otherwise workmanlike midfield, Aiden McGeady is one of the few players capable of producing the unexpected. Spartak Moscow are believed to have paid Celtic at least £9.5m for the left winger in 2010, making him the most expensive export from Scottish football.
The Glasgow-born player is eligible for the Republic through his Donegal-born grandmother.
Handed his Ireland debut in 2004, he failed to score in his first 37 international appearances.
However, he netted twice in qualifying (against Macedonia and Andorra), albeit both goals were aided by heavy deflections.CROATIA
HOW DO THEY PLAY?
Croatia have struggled to replace brothers Robert and Niko Kovac, who were key players and the spirit of the team. They have problems at the back, too, because Jo Simunic is not playing regularly and is out of form. This means a lot of the responsibility will fall on star midfielder Luka Modric. He is an outstanding talent but like at Tottenham, he doesn't score too many goals. He will dictate Croatia's tempo yet the question remains whether his team-mates can finish off his creativity.
Likely formation: 4-4-2
Possible starting XI: Stipe Pletikosa; Vedran Corluka, Gordon Schildenfeld, Josip Simunic, Ivan Strinic; Darijo Srna, Tomislav Dujmovic, Luka Modric, Niko Kranjcar; Mario Mandzukic, Ivica Olic.
Easily one of the best midfielders in the Premier League, Luka Modric (pictured right) might also be described as one of the best players in the world. Tottenham dug their heels in to stop Modric from moving to Chelsea last summer, and have been rewarded as he continues to lead them on an upward curve with a heady blend of creation and vision.
Spurs clinched his signature shortly before Euro 2008, where Modric's majestic midfield displays saw him chosen in Uefa's team of the tournament. He converted a penalty in Croatia's opening win against Austria, but dragged his spot-kick wide in the shoot-out loss to Turkey. The 26-year-old will be desperate to make amends this summer.
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Croatia's captain Darijo Srna has been a regular on the right flank for almost a decade, and is probably their second-best player behind Modric. Mainly used by Shakhtar Donetsk as an attacking right-back, he was deployed on the right wing by Slaven Bilic during the latter stages of Croatia's Euro 2012 qualifying campaign.
Srna has an excellent goalscoring record, and was on the scoresheet at both the 2006 World Cup and Euro 2008.
He was briefly dropped by Bilic after visiting a nightclub before a qualifier in 2006, but three years later was handed the captain's armband following Niko Kovac's retirement.