The 21-year old former Stanford University star was taken with pick number nine in January's draft and has now been signed by the Quakes after impressing in preseason training.
Koval is a central midfielder who played four seasons with the Cardinal where he earned All-Pac 12 honours and also spent time with the Ventura County Fusion last season in the United Soccer League's PDL - the fourth tier of the American soccer pyramid.
"I'm very excited. It's been a dream of mine to get an opportunity to play professional soccer for a long time," Koval said.
"I'm thankful for the chance and look forward to playing for the San Jose Earthquakes."
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