The Cubs selected Assad's contract from Triple-A Iowa ahead of his scheduled start in the first game of Tuesday's doubleheader with the Cardinals, Meghan Montemurro of the Chicago Tribune reports.
Outfielder Jason Heyward (knee) was transferred from the 10-day IL to the 60-day injured list to clear room on the 40-man roster for Assad, who will be making his MLB debut Tuesday. Assad will likely just be in line for a spot start before heading back to Iowa, though he could change the Cubs' plans for him if he fares better than expected against a hot-hitting St. Louis lineup. Over his 36.2 innings at Iowa since receiving a promotion from Double-A Tennessee earlier this summer, Assad produced a 2.95 ERA, 1.05 WHIP and 37:7 K:BB.