During the summer of 2018, McLain played in the West Coast League for the Bellingham Bells, and was awarded the Top Prospect Award.[7] As a freshman at UCLA in 2019, he appeared in 61 games (with sixty being starts) in which he slashed .203/.276/.355 with four home runs and thirty RBIs.[8] That summer, he played collegiate summer baseball with the Wareham Gatemen of the Cape Cod Baseball League, and was West division MVP of the league's all-star game.[9][10] In 2020, McLain played in 13 games and batted .397 with four home runs before the season was cancelled due to the COVID-19 pandemic.[11] In 2021, he missed three weeks due to a fractured thumb, but still hit .333 with nine home runs and 36 RBIs in 47 games.[12]
McLain made his professional debut with the Rookie-levelArizona Complex League Reds and was promoted to the Dayton Dragons of the High-A Central.[15] Over 31 games between the two teams, he slashed .283/.389/.462 with three home runs, 19 RBIs, and ten stolen bases.[16]
For the 2022 season, he was promoted to the Reds' Double-A affiliate, the Chattanooga Lookouts.[17] In 103 games for Chattanooga, McLain slashed .232/.363/.453 with 17 home runs, 58 RBI, and 27 stolen bases. McLain was assigned to the Triple-A Louisville Bats to begin the 2023 season. In 38 games, McLain hit .348/.474/.710 with 12 home runs, 40 RBI, and 10 stolen bases.
On May 15, 2023, the Reds announced that McLain would be promoted to the major leagues for the first time the following day.[18] In 89 games for Cincinnati, he batted .290/.357/.507 with 16 home runs, 50 RBI, and 14 stolen bases.[19] On August 28, McLain was placed on the injured list with a right oblique strain.[20] He began a rehab assignment with Triple–A Louisville on September 23,[21] however he was shut down for the season on September 26 after aggravating the injury.[22]
On March 26, 2024, McLain underwent shoulder surgery to repair the labrum and some damaged cartilage, ruling him out indefinitely.[23]
Personal life
McLain's brothers, Nick and Sean, also play professional baseball.[24]