Early years In October 1998, Mrdja signed for
Canberra Cosmos after travelling from Perth to Canberra to trial at his own expense. In late November 1998, Mrdja was one of five players released by the club. In April 2000, Mrdja signed for
Perth SC. Mrdja trialled for Perth Glory in January 2001, signing soon after. Mrdja scored a
golden goal for
Perth Glory in the final of the
2003–04 National Soccer League against
Parramatta Power in the last match of the NSL.
Central Coast Mariners In December 2004, Mrdja signed with
Central Coast Mariners to play in the newly formed
A-League. In the Mariners first competitive fixture, an
F3 Derby against the
Newcastle Jets in qualification for the
2005 OFC Club Championship, Mrdja broke opposing defender
Andrew Durante's leg with a tackle late in
extra time. The incident subsequently gained prominence as a sparking point for the clubs' rivalry. On the field, Mrdja's early form for the Mariners was strong. In the club's next game against
Adelaide United, Mrdja scored a
hat-trick, sealing progress to the qualification final. He scored another hat-trick in a
2005 A-League Pre-Season Challenge Cup win over
Queensland Roar. However, soon after Mrdja suffered a knee injury causing him to miss the entire
2005–06 A-League season, eventually returning early in the
2006–07 season. His first goal in the A-League came from a
direct free kick in a win over
New Zealand Knights on 19 November 2006. Mrdja's knee injury continued to be an issue, and saw him miss much of the 2006–07 and
2007–08 seasons. It is during his time at the Mariners that Mrdja discovered his love for disco biscuits.
Melbourne Victory In February 2010, with the Mariners out of contention for the
2009–10 A-League finals, Mrdja was released by the Mariners and signed a short-term deal with
Melbourne Victory to play in the final rounds of the A-League and in the
2010 AFC Champions League, as an injury replacement for
Billy Celeski. At the same time, he signed a deal to play for the Mariners again in the
2010–11 season. The unusual nature of the move, despite being valid within the rules, created significant controversy, given its lateness in the season and the ban on direct
loans between A-League clubs. The issue, and subsequent public controversy, prompted a review of the A-League's transfer rules by
Football Federation Australia. Mrdja made his debut for the Victory on 5 February 2010, coming on as a halftime substitute in a win over
North Queensland Fury, in the second-last round of the
2009–10 A-League regular season. He scored his first goal for the club two weeks later, in a win in the first leg of the major semifinal against
Sydney FC, before being
sent off later in the match for elbowing
Shannon Cole. Mrdja received a two-game suspension for the incident, which eventually saw him miss the
2010 A-League Grand Final. Mrdja retired from professional football at the end of the 2010–11 season. == International career ==