Alexander was promoted to Triple-A Toledo on Friday, Emily Waldon of The Athletic Detroit reports.
Alexander -- a 2015 second-round pick -- has been at Double-A Erie since the end of the 2016 season, and has a 3.75 ERA and 1.52 WHIP with 35 strikeouts and nine walks over 48 innings for the SeaWolves this season. The 23-year-old has allowed seven home runs and a .325 opponent batting average, but will nonetheless head to the Triple-A level for the first time in his career.