We check out the significance of the number 25 in our countdown to the opening game of the 2012-13 Hyundai A-League season.

Two Melbourne Heart players have celebrated their 25th birthdays already this year, with defender Michael Marrone and new Croatian signing Josip Tadic clocking over the quarter-century mark in 2012.

Marrone has featured in the A-League since his debut on 25 January 2009 for Adelaide United, against Central Coast Mariners. Michael played 26 games for Adelaide United before signing with Heart on 30 April 2010.

Tadic will feature in his first A-League campaign in season 2012-13 after a promising career in Europe, which included 25 appearances for Bayer Leverkusen-s reserves side, scoring six goals, before earning one senior appearance.

But Tadic-s most successful stint in Europe came at Croatian club Dinamo Zagreb, where he earned 62 appearances and netted 20 goals, contributing to three consecutive titles and featuring in UEFA Champions League qualifying and the UEFA Cup.

Between 2008-09, new Heart goalkeeper Andrew Redmayne made 25 appearances for Australia-s under-20 side, the Young Socceroos.