 Keizer made her international beach volleyball debut at the 2002 U18 European Championships in August, where she and Arjanne Stevens won the silver medal.Two weeks later, the pair became the inaugural U18 World Champions with an unbeaten tournament run in Xylokastro, Greece.Following her success on the junior circuit, Keizer debuted on the FIVB World Tour in 2003, partnering with Merel Mooren at the $150K Hellas Open in June.