With 100 days to go until Euro 2012, the leading candidates for the title will approach Wednesday's friendly games knowing that this will be their last opportunity to experiment until the end of the season.
Some, like Italy, Germany and England, have had changes imposed upon them by injuries, but others, like defending champions Spain, have been obliged to re-evaluate their resources after setbacks in recent matches.
Spain are bidding to become the first team to win back-to-back European Championship titles, but their results since lifting the World Cup in 2010 have quietly begun to erode their aura of invincibility.
Although imperious in qualifying for Euro 2012, Vicente del Bosque's side have come unstuck in non-competitive matches, having lost heavily to Argentina and Portugal in 2010 before going down to Italy and England last year.
Their last outing saw them scrape a 2-2 draw with Costa Rica in November and Del Bosque reacted by making several adjustments to his squad for Wednesday's game with Venezuela at La Rosaleda in Malaga.
Goal-shy Chelsea striker Fernando Torres has been overlooked by his country for the first time since November 2006, while Barcelona's Pedro Rodriguez was also left out after several months disrupted by injuries.
Athletic Bilbao youngster Iker Muniain and Valencia striker Roberto Soldado were the chief beneficiaries, but Del Bosque warned that the squad "was not a definitive list in anticipation of the Euro".
With Spain's mantle slipping, Joachim Loew's young Germany team are widely seen as the side most likely to seize their crown in Poland and Ukraine.
Germany finished their qualifying campaign with a perfect record of 10 wins and impressed in their last friendly outing in November, when they slickly dismantled World Cup finalists the Netherlands 3-0 in Hamburg.
The three-time European champions meet France in Bremen on Wednesday, when injuries to Philipp Lahm, Per Mertesacker, Bastian Schweinsteiger, Mario Goetze and Lukas Podolski will oblige Loew to overhaul his preferred starting XI.
"Despite the injuries, there is no intention to make big changes," said Loew.
"Preparations for previous tournaments have shown that it makes little sense to give a detailed prognosis of who will ultimately be in the squad in February."
Laurent Blanc's France, who edged Bosnia-Herzegovina to top spot in qualifying Group D, have also been hampered by injuries, with key strikers Karim Benzema and Loic Remy both ruled out of the game in Bremen.
Italy, too, have problems in attack, with injury and ill health robbing coach Cesare Prandelli of strikers Giuseppe Rossi and Antonio Cassano.
Prandelli also chose to omit Mario Balotelli for Wednesday's encounter with the United States in Genoa, after the Manchester City forward had to serve a four-match ban for a stamp on Tottenham Hotspur's Scott Parker.
"I don't want players who commit reaction fouls and get sent off," Prandelli explained at the weekend.
England's preparations for Euro 2012 were rocked by the resignation of coach Fabio Capello, meaning under-21 coach Stuart Pearce will be in the dug-out for the game against the Netherlands at Wembley.
Fitness concerns have not spared the Three Lions either, with strikers Wayne Rooney and Darren Bent and emerging Manchester United midfielder Tom Cleverley among the players ruled out of Wednesday's match.
Elsewhere, Ukraine visit Israel and fellow co-hosts Poland tackle Cristiano Ronaldo's Portugal, while Feyenoord's on-loan Manchester City striker John Guidetti is set to make his Sweden debut against Croatia in Zagreb.
There will be a sombre mood, meanwhile, at Wales' encounter with Costa Rica in Cardiff, which is being played as a memorial match to late Wales manager Gary Speed.