Diaz, 19, has batted .208 (5-for-24) with three doubles and four RBI in seven games for short-season Single-A Lowell in 2017, making five starts at shortstop and one at second base. Signed by Boston as an international free agent on July 2, 2014, the Venezuelan native has hit .222 (105-for-472) with a .538 OPS in 123 career minor league games, all in the Red Sox organization.
Espinal, 20, has hit .185 (5-for-27) with a pair of doubles in seven games with Lowell, all starts at third base. The Dominican Republic native was signed by Boston as an international free agent on February 3, 2015. In three seasons in the Red Sox organization, he has hit .251 (132-for-525) with 28 doubles, seven triples, eight home runs, and a .682 OPS in 132 career minor league games.