Germany 
Already a key man in the German line-up despite his relative youth, Mertesacker's defensive partnership with Christoph Metzelder was the main reason they conceded just seven goals throughout qualifying.
Capped over 40 times since making his debut as a somewhat raw 19-year-old in October 2004, he has been the glue that has held Germany's defence together pretty much ever since, no matter who his partner.
Having broken through at Hannover, Mertesacker built his reputation with his boyhood heroes and attracted interest from around Europe after playing a starring role for his country at the 2006 World Cup on home turf.
He eventually opted to join Werder Bremen in a 5million euro move, though more recently he found himself linked with a big-money switch to Aston Villa.
A certain starter, injury permitting, Mertesacker's height makes him understandably strong in the air both defensively and in attack, while he is also good enough on the ball to start attacks from the back.
Expect some of Europe's biggest clubs to be monitoring his performances this summer with interest - if they aren't already.
