[1] Espinoza signed with the Boston Red Sox as an international free agent in October 2014, receiving a reported bonus of $1.8 million plus $200,000 in scholarship money.

Additionally, Espinoza was Baseball America’s fourth-ranked international amateur prospect and top-ranked pitcher, while grabbing the number 10 spot on MLB.com’s list.

He made quick work of that circuit, allowing only two earned runs on 13 hits and two walks for a 1.20 ERA, while striking out 21 batters in 15 innings.

[4] Instead of finding himself challenged, Espinoza was even more dominant there, giving up just three earned runs in 40 innings, good for a 0.68 ERA to go with a .170 opponents batting average and 40 strikeouts against nine walks,[1] helping the GCL Red Sox clinch their second title in a row.

The precocious right-hander completed his third level of the season with his promotion to the Low-A Greenville Drive, and made his first pitching appearance on September 5.

With his debut, Espinoza became the first pitcher in his age 17 season to make a start in the full-season Class A South Atlantic League since 2006, when Deolis Guerra did it for the New York Mets affiliate Hagerstown Suns.

[1] On July 14, 2016, the Red Sox traded Espinoza to the San Diego Padres in exchange for pitcher Drew Pomeranz.

[16][17] On December 12, 2022, Espinoza signed a minor league deal with an invitation to spring training with the San Diego Padres.