Wozniacki had a career-high junior ranking of No. 2 in the world. She made her debut on the ITF Junior Circuit, the premier 18-and-under junior tour that is run by the International Tennis Federation (ITF), in October 2003 at 13 years and 3 months old. During her first month, she entered two Grade 5 events in Denmark, the lowest-level tournament on the tour. Wozniacki reached the final at both singles events, winning the second over compatriot Hanne Skak Jensen. With this success, she moved up to Grade 3 and Grade 4 tournaments, winning her first four singles events of 2004. Her win streak of five tournaments and 27 matches came to an end in April with a semifinal loss to Latisha Chan at the International Juniors Championships in Manila, her first event outside of Scandinavia as well as her first Grade 1 event. From this point on, Wozniacki only competed in Grade A and Grade 1 events, the two highest-level tournaments. She made her Grade A debut at Wimbledon before turning 14, losing her first main draw match. Towards the end of the year, Wozniacki won her first Grade A title at the Osaka Mayor's Cup.