With the Railroaders 2020 season cancelled due to COVID-19, Simpson was selected by the Milwaukee Milkmen with the first overall pick of the American Association dispersal draft. He played in five games with the Milkmen, recording five hits, before missing the remainder of the season with an injury.
Simpson delivered a record-breaking 2019 season, establishing new franchise marks for single-season home runs and RBI. He finished the year with a .272/.390/.536 slash line, blasting 20 home runs and leading the American Association with 93 RBI.
Simpson had a productive and well-traveled 2018 season, splitting it between Cleburne, the Lincoln Saltdogs, and the Wichita Wingnuts. In 99 total games, Simpson hit .273 with 22 doubles, 13 home runs and 47 RBI. The switch-hitter led the American Association with 75 walks, 13 more than the next closest player, finishing the year with a .401 on-base percentage.
The 27-year old began the year with Lincoln and got off to a blistering start, hitting .413 through the first two weeks of the season. On July 6, he was traded to Cleburne in exchange for right-handed pitcher Cortland Cox, ultimately playing in 26 games with the Railroaders. Simpson hit .284 with two home runs while donning the orange and navy, walking 24 times to 23 strikeouts. Wichita acquired Simpson from Cleburne on August 1 in exchange for outfielder Hunter Clanin and a player to be named later, which would turn out to be Simpson himself.
Simpson played collegiately for Weatherford College and the University of Oklahoma before finishing his career with Wichita State University in 2014, hitting .258 with 14 doubles, six home runs and 41 RBI as a junior. He was selected by the Pittsburgh Pirates in the 14th round of the MLB Draft, and spent parts of four seasons in the Pirates minor league system. Simpson reached Double-A Altoona in 2017, but was released and joined the independent ranks with the York Revolution of the Atlantic League.