A busy weekend of friendly action will be the final chance for many players to secure a ticket on the plane for Euro 2012 before the UEFA deadline for squad submissions next Tuesday.
Reigning European champions Spain take on Serbia in the Swiss town of St Gallen with a host of fringe players expected to get their chance to impress coach Vicente Del Bosque.
With several integral members of the Spain squad due to play in Friday's Spanish Cup final between Barcelona and Athletic Bilbao, the door is open for the likes of Atletico Madrid duo Juanfran and Adrian Lopez, Isco of Malaga and Sevilla striker Alvaro Negredo to stake their claim.
"There is always healthy competition for places in the national squad," insists Negredo.
"Everyone here has come to try and win a place at the Euros. We are competing with world-class players in every position so you just have to work hard and make sure the coach sees you are ready if and when needed."
The biggest challenge to Spain's defence of the Euro crown is expected to come from Germany, and Joachim Loew's side are in action on Saturday against Switzerland in Basel.
Four men will have to be dropped from Loew's initial 27-man list next week, so the likes of Borussia Dortmund's Ilkay Gundogan and Schalke's Julian Draxler will know that it is now or never for them.
Meanwhile, the Netherlands - in Group B at Euro 2012 along with Germany - host Bulgaria in Amsterdam.
Coach Bert van Marwijk took a 27-man squad with him to a training camp in Lausanne, Switzerland and oversaw a 3-2 friendly win against Bayern Munich on Tuesday.
However, he has admitted that he may announce his final squad before facing Bulgaria.
The Oranje begin their Euro 2012 bid against Denmark on June 9, and the Danes face Brazil in the German city of Hamburg on Saturday.
Danish coach Morten Olsen will not be experimenting here, however - he named his final 23-man Euro squad on Thursday.
World Cup 2014 hosts Brazil are using this game as part of their preparations for the London Olympics.
England take on Norway in Oslo in their first game since Roy Hodgson was appointed as coach.
Hodgson only directed his first training session on Wednesday but will want a positive result as European Championship preparations are stepped up.
Frank Lampard is one of several members of the squad to have come straight from winning the Champions League with Chelsea and is hoping that success can rub off on his England colleagues.
"If we can bring some of the play, the spirit, the determination - whatever it is that's won us the Champions League - into the England team then hopefully that can help this summer," Lampard said.
France entertain Iceland on Sunday in the first of three friendlies that coach Laurent Blanc has lined up ahead of their opening Euro 2012 match against England on June 11.
"We will make a significant number of changes to the team in the game against Iceland," Blanc said.
"After that we will see. Our aim is to know what the majority of our likely starting line-up to face England will be by the time we play Estonia in our last friendly."
Elsewhere, the Republic of Ireland host Bosnia-Herzegovina with coach Giovanni Trapattoni likely to be without several first-choice players.
Defenders Richard Dunne, John O'Shea, Kevin Foley and Sean St Ledger are doubts, while goalkeeper Shay Given is also recovering from a knee injury.
"I think he wishes to play, but if he plays and he then has a problem..." Trapattoni said. "Our Euros begin in Poland, not in Dublin or in Hungary (Ireland's next friendly opponents)."
Ireland's opening Euro 2012 Group C opponents Croatia entertain Estonia on Friday, while Russia face Uruguay.
Portugal host Macedonia, while Euro 2012 co-hosts Poland face Slovakia, the Czech Republic take on Israel and Greece meet Slovenia in other games on Saturday.
Ukraine face Estonia on Monday.