Goalkeeper who appeared in 367 matches for Middlesbrough from 1997 to 2008 and became Australia's most capped player with 109 between 1993 to 2013.
He started his professional senior career with the Marconi Stallions, in the National Soccer League.
He played for Australia in both the 2006 and 2010 World Cups, and led his team to second place in the 2011 Asian Cup.
His parents were German immigrants to Australia, migrating over in 1968.
He joined Frank Lampard on Chelsea in 2013.