The 26-year-old tested positive for a performance-enhancing substance called Boldenone.
Reyes appeared in 71 games for the Pirates in 2019—most recently the team's regular-season finale on Sept. 29—and posted a .203/.274/.322 slash line for two home runs and 19 RBI across 143 plate appearances. He started 24 games in the outfield.
The Dominican Republic native made his major league debut on Sept. 2, 2018. He recorded 18 games with Pittsburgh to finish out the 2018 season, batting .293 with three home runs and seven RBI.
The Pirates have issues to sort out beyond Reyes' suspension. The franchise has not made the postseason since 2015 and finished last season at 69-93, the second-worst mark in the National League.