Imanaga is no longer listed as the Cubs' starting pitcher for Thursday's game in St. Louis, Meghan Montemurro of the Chicago Tribune reports.
Imanaga is not dealing with any known injury, so this appears to simply be about giving him and the other members of the Cubs' normal rotation some extra rest. Javier Assad will make a spot start Thursday against the Cardinals, and Imanaga presumably will now take the ball versus the Yankees at Wrigley Field on Friday.