Kaprielian attended Arnold O. Beckman High School in Irvine, California. During his career he went 33–3 with a 0.96 earned run average and 250 strikeouts. He was drafted by the Seattle Mariners in the 40th round of the 2012 Major League Baseball Draft. He did not sign with the Mariners and enrolled at the University of California, Los Angeles to play college baseball for the UCLA Bruins. As a freshman in 2013, Kaprielian appeared in 34 games as a relief pitcher, recording a 1.55 ERA with 53 strikeouts. In 2013, he played collegiate summer baseball in the Cape Cod Baseball League for the Yarmouth-Dennis Red Sox, and was named a league all-star. As a sophomore, he was converted into a starter. He started 15 games, going 7–6 with a 2.29 ERA and 108 strikeouts. On May 15, 2015, Kaprielian combined with David Berg for the first no-hitter in UCLA history. Kaprielian pitched the first nine innings and Berg pitched the tenth inning to complete the no-hitter.
Kaprielian was considered one of the top prospects for the 2015 Major League Baseball Draft, and was selected by the New York Yankees in the first round, with the 16th overall selection. He signed with the Yankees, receiving a $2.65 million signing bonus, and spent his first professional season with both the GCL Yankees and Staten Island Yankees, posting a combined 0-1 record and 3.97 ERA in total innings between both teams. Kaprielian received a non-roster invitation to spring training in 2016. He began the season with the Tampa Yankees, but only played in three games due to an elbow injury. In 2017, Kaprielian's elbow discomfort began to persist, and he began the season on the disabled list. On April 13, 2017, it was revealed that Kapielian would undergo Tommy John surgery to repair a torn ulnar collateral ligament, putting him away for the year.
On July 31, 2017, the Yankees traded Kaprielian to the Oakland Athletics, along with fellow prospects Jorge Mateo and Dustin Fowler, for Sonny Gray. The Athletics added him to their 40-man roster after the 2018 season. On May 19, 2019, Kaprielian made his debut at High-A Stockton. He accumulated a 4.46 ERA in 36.1 innings with a 43:8 K-to-BB ratio before the Athletics promoted him to Double-A Midland on July 23.
Personal life
Kaprielian's mother, Barbara Kaprielian, died of breast cancer in 2014 after her 14-year battle. Kaprielian is of Armenian descent.
