[1] Koval was drafted ninth overall in the 2014 MLS SuperDraft by the San Jose Earthquakes.

On March 11, 2014, Koval made his professional debut for the Earthquakes in a CONCACAF Champions League match against Toluca, coming on for Jason Hernandez in the 73rd minute.

[3] After spending the 2016 season with the Sacramento Republic, Koval announced his retirement from professional soccer on December 21, 2016, to pursue a career in dentistry at Creighton University School of Dentistry in Omaha, Nebraska.

[5] Koval also credits much of his later personal development to a friend whom he met in Omaha, Nebraska during dental school: Austin Gouldsmith.

He helped a local Omaha resident Levi Gipson reduce molar wear by recommending less popcorn kernel gnawing, and he also served in Los Cerezos, Dominican Republic; there he completed two weeks worth of extractions, cleanings, and fillings at a makeshift dental clinic set up in the local school.