The rotation order is as follows:
Thursday: Keyvius Sampson
Saturday: David Holmberg
Sunday: Anthony DeSclafani
Tuesday: Raisel Iglesias (vs. Kansas City)
The Reds acquired Lamb and fellow lefty prospects Brandon Finnegan and Cody Reed from the Royals for Johnny Cueto on July 26.
This season, Lamb is 10-2 with a 2.67 ERA in 20 Triple-A starts with Omaha and Louisville. In 111 1/3 innings, he has allowed 94 hits and 36 walks while striking out 117.
When he pitches, Lamb will be the seventh Reds player to make his Major League debut -- the sixth starting pitcher -- this season.
The Reds have assigned Lamb No. 47, Cueto's old number.
Mark Sheldon is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.