Howell made his professional debut with the Rookie-level Arizona League Brewers, batting .311/.398/.350 over 28 games. In 2019, he played with the Wisconsin Timber Rattlers of the Class A Midwest League with whom he hit .235 with two home runs, 22 RBIs, 12 doubles, and 19 stolen bases over 91 games. He did not play a minor league game in 2020 after the cancellation of the season due to the COVID-19 pandemic, and spent the summer playing with the Joliet Slammers of the independent Frontier League. To begin the 2021 season, he was assigned back to the Timber Rattlers, now members of the High-A Central. He was promoted to the Biloxi Shuckers of the Double-A South in early August. Over 107 games between the two clubs, he slashed .244/.349/.455 with 16 home runs, 51 RBIs, and 24 stolen bases.
