The Reds selected McLain's contract from Triple-A Louisville on Monday.
McLain is expected to take over as the Reds' primary shortstop while also seeing the occasional start at second base. He slashed .346/.464/.713 to go with 12 home runs and 10 stolen bases across 168 plate appearances with Louisville this season and will get to break in at the major-league level at Coors Field for his first series. McLain is worth rostering in most formats where he might be available.