Less than a year after leaving high school at Wellington's Scots College, Riddle shot to prominence after a high-scoring debut season with Wellington United in the New Zealand Superclub competition. At the age of 19, Riddle was the youngest member of Bobby Clark's 1996 New Zealand Olympic Team where he made four appearances including one as a substitute in a 1–0 victory over then Oceania rivals Australia where ex-Fulham midfielder Simon Elliott scored the only goal of the game at Adelaide's Hindmarsh Stadium. After brief stints with several clubs including Chelmsford City in the UK, Riddle turned to the US college system and spent two years with the Myrtle Beach-based Coastal Carolina University before being signed by Kiwi football iconWynton Rufer for the Kingz debut season in the National Soccer League in 1999. Although he signed a two-year contract, Riddle struggled to regularly feature in the Kingz side and only managed nine appearances with a return of two goals, both of which came away from home against Adelaide United and Brisbane Strikers. Better form would be found in the lower United States leagues with Riddle being a mainstay of the Laurie Calloway-coached Des Moines Menace side that would achieve an undefeated season in the 2002 USL Premier Development League competition. Riddle turned to the UK again in the hope of being signed by a Football League side but again struggled with the higher level of play and had short spells at Oxford City and Greenock Morton before being reunited with former Kingz teammates Marcus Stergiopoulos and Levent Osman at the Melbourne-based Altona Magic in the Victorian Premier League. Despite a good scoring record he fell out of favour with the management of the Macedonian flavoured club and returned to the United States.
Management career
In 2006, he became a coach in the United Soccer Leagues when he accepted a player-coaching job with Kalamazoo Kingdom in the USL Premier Development League, United States elite development league. In 2008, he served as the head coach for the Kalamazoo Outrage in the USL Premier Development League, United States elite development league team in the franchises inaugural year. On 13 July 2008 the Kalamazoo Outrage qualified for the 2008 USL Premier Development League playoffs in their inaugural year. Riddle guided his side to second place in the Central Conferences Midwest Division narrowly finishing behind the Chicago Fire Premier in the regular season standings. His side would get their revenge eliminating the Chicago Fire Premier from the 2008 playoffs by virtue of a 2–0 victory at Toyota Park on 22 July. Their fairytale run would continue under Riddle and they defeated perennial USL Premier Development League powerhouse the Michigan Bucks on 26 July to advance to the national quarter finals where the Thunder Bay Chill would end the Outrage's season. Riddle became the sixth head coach of Western Michigan University when he was named the men's soccer coach on 30 January 2009. With this announcement he became the first New Zealander to be a head men's soccer coach at the National Collegiate Athletic Association Division I level.
Personal
Riddle graduated with a Bachelor of Science in Physical Education from Coastal Carolina University in 1999. He earned his master's degree in public service administration from the University of Evansville in 2007 while serving as an assistant coach for the Purple Aces. Born in England and raised in New Zealand, Riddle became a naturalized U.S. citizen at a ceremony in Grand Rapids, Michigan on August 16, 2011. He and his wife, Jessica, have two daughters, Rylee Noelle and Nora Jane.
