Harold Castro was signed by the Tigers in 2010 as a 16-year-old. Castro spent 2011 and 2012 with the Tigers' Venezuelan summer league team, then a half-season with the Gulf Coast Rookie League team. In 2013, he played for the single-A West Michigan Whitecaps and single-A advanced Lakeland Flying Tigers, where he hit.245. He improved to a.286 average the next season, playing for the same two teams. Castro spent the entirety of the 2015 and 2016 regular seasons, and all but eight games of 2017, with the Double-AErie SeaWolves. Castro's 2017 with Erie was his best at the level. He hit for a.290 average, with a.325 on-base percentage, one home run, 30 RBI, and 20 stolen bases. During the 2018 season, Castro spent 74 games with the Triple-AToledo Mud Hens and hit for a.257 average with two home runs and 17 RBI. He also played 29 games with the SeaWolves, where he had a.282 average with ten RBI.
Detroit Tigers: 2018
On September 21, 2018, the Tigers purchased Castro's minor league contract and added him to the roster after he had spent the last eight years in their minor league system. Since the Mud Hens season had already ended, Castro had to travel back to Detroit from his home in Venezuela. He made his major league debut on September 23, as a pinch runner in the ninth inning of a game against the Kansas City Royals. He made his first MLB start on September 25, against the Minnesota Twins, where he recorded his first major league hit, a single in the top of the eighth inning. He went 3-for-10 in his brief 2018 stint with the Tigers. Castro was outrighted to Toledo on October 24 and elected free agency. He re-signed a minor league deal on October 31, 2018, with an invitation to spring training.
2019
Castro opened the 2019 season with Triple-A Toledo. On April 30, after hitting.353 for the Mud Hens, his contract was selected and he was recalled to the major league roster. He was optioned back to Toledo on May 13, then recalled again to the Tigers on June 4. On June 19, he hit his first career major league home run offTrevor Williams of the Pittsburgh Pirates. During the 2019 season, Castro played every fielding position except pitcher and catcher. In 354 at-bats for the Tigers, Castro hit.291 with 5 home runs and 38 RBI. Castro was named the 2019 Detroit Tigers Rookie of the Year in voting conducted by Detroit Sports Media association.
