Walker returned to Kannapolis to begin the 2019 season.[13] In late April, Walker was promoted to the Winston-Salem Dash of the High–ACarolina League after batting .365 in 20 games.[14] On June 14, Steele hit for the cycle.[15] He spent the remainder of the season with the Dash, slashing .269/.346/.426 with ten home runs and 51 RBIs over 100 games.[16][17]
Walker opened the 2021 season with the Frisco RoughRiders of the Double-A Central league. He was promoted to the Round Rock Express of the Triple-A West league on August 5.[19] Between the two levels, he hit a combined .241/.308/.400 with 15 home runs (none against left-handers) and 61 RBI.[20] Walker returned to Round Rock to open the 2022 season.[21]
On June 5, 2022, Texas selected Walker's contract to the active roster and promoted him to the major leagues for the first time. He made his MLB debut that day versus the Seattle Mariners.[22] On June 7, Walker hit his first career home run as his first major league hit off of Cal Quantrill of the Cleveland Guardians.[23]
In the minor leagues to that point, on defense he had played 147 games in center field, 71 games in right field, and 55 games in left field.[1]
San Francisco Giants
On August 7, 2022, Walker was claimed off waivers by the San Francisco Giants.[25] The Giants assigned him to the Triple-A upon acquiring him.[26] Walker was designated for assignment on August 17. He cleared waivers and was sent outright to the Triple-A Sacramento River Cats.[27]
Detroit Tigers
On November 15, 2022, Walker was traded to the Detroit Tigers for cash considerations. He split the 2023 season between the rookie–level Florida Complex League Tigers, High–A West Michigan Whitecaps, and Triple–A Toledo Mud Hens. In 28 total games, he accumulated a .202/.288/.317 batting line with 2 home runs and 14 RBI.[28] On July 10, 2023, Walker was released by the Tigers organization.[29]