McGuire will make his first major-league start Tuesday against the Brewers, Mark Sheldon of MLB.com reports.
Rookie Davis was originally scheduled to take the mound Tuesday against the Brewers, but he has been shut down for the season with a hip impingement. His injury now opens up an avenue for McGuire to join the starting rotation over the final days of the regular season. The 28-year-old has tossed 5.2 innings of scoreless relief for the Reds in September and held a solid 2.79 ERA over 168 innings with Double-A Pensacola prior to his contract selection earlier this month. He'll face a tough matchup at hitter-friendly Miller Park on Tuesday, so he can comfortably be left off the fantasy radar.