Due to a shoulder injury for Evgeniya Ukolova that forced her to withdraw from the 2017 FIVB World Championships with Anastasia Barsuk, the Dutch team was awarded the Russian team's spot in the event after qualifying via the European Continental Cup process. With Flier-Nummerdor playing her first season on the FIVB World Tour, van Iersel has been competing in international events since 2003. Van Iersel has competed in four previous FIVB World Championships with two different partners (Sanne Keizer in 2009, 2011 and 2013) and Madelein Meppelink in 2015) with a best finish of fifth in 2009 followed by three-straight ninths. Van Iersel netted four medals in nine FIVB youth world championships highlighted by a 2008 under-21 title with Danielle Remmers. Van Iersel and Keizer, who captured two FIVB World Tour gold medals together in May 2011, placed ninth at the London 2012 Olympics. Van Iersel and Meppelink also placed ninth at the Rio 2016 Olympics. Married to Reinder Nummerdor, Nummerdor-Flier played 15 seasons on the Dutch National team and took the 2016 season off to give birth to her first child in July. She started playing Beach Volleyball for the first-time on the FIVB World Tour this season.