Robert "Bobby" Costello started riding in as a child in Massachusetts, competing at local shows and fox-hunting with the Myopia Hounds. He found the sport of eventing and worked his way through the ranks as a professional, ultimately competing at the highest levels in the sport of eventing.

Costello became an upper-level staple for the program, representing the U.S. Eventing Team at the 2000 Sydney Olympic Games in Sydney Australia, taking eighth individually with Chevalier. The pair also secured top results at Bughley CCI5*-L and the Rolex Kentucky Three-Day Event. Costello finished seventh individually at the 2003 Pan American Games with Dalliance, before turning towards coaching and eventually stepping away from riding full-time in 2010 and focusing solely on coaching and training. 

Since he joined the program in 2022, Costello has helped several senior teams produce significant results at major international competitions and championships including a team silver at the 2022 FEI Eventing World Championships in Pratoni del Vivaro, Italy, and a team silver at the 2023 Pan American Games in Santiago, Chile. Under Costello's tutelage, the team has also secured two-consecutive second-place finishes in the CCIO4*-S at CHIO Aachen in 2023 and 2024. 

Phillip Dutton began riding horses on his family farm while growing up in Australia. He moved to the U.S. in 1991 to prepare for the Atlanta 1996 Olympic Games and continued representing his native country until 2006, when he became a U.S. citizen. Dutton has been a mainstay on U.S. teams ever since.

Dutton has competed in every Olympic Games since 1996, winning team gold with Australia in 1996 and 2000, and as a member of the U.S. team in 2008, 2012, 2016, and 2020. He won individual bronze with Mighty Nice at the 2016 Olympics in Rio de Janeiro. He has competed in seven FEI World Equestrian Games, representing the U.S. for the first time in 2006. He won team gold and individual silver at the 2007 Pan American Games with Truluck and team gold at the 2015 Pan American Games with Fernhill Fugitive.

Dutton has been the top-finishing American at the Kentucky Three-Day Event several times, winning the USET Foundation Pinnacle Cup in 2017 with Mr. Medicott, 2015 with Fernhill Cubalawn, 2010 with Woodburn, and 2007 and 2008 with Connaught. In 2008, he was also the overall winner of the event.

Recently, Dutton and Z were fourth at the 2022 Maryland 5 Star CCI5*-L and fifth at the 2023 Land Rover Kentucky Three-Day Event presented by MARS Equestrian^TM CCI5*-L.

Dutton resides in Pennsylvania with his wife Evie, twin daughters, Mary and Olivia, and stepdaughter Lee Lee.