Colorado has off-days June 24 and July 1, so it could delay the decision a couple more times through the rotation.
Tuesday is the first of the dates that the Rockies must determine whether to add Oswalt to the Major League roster within days or allow him to look at other clubs. The chances of the Rockies losing Oswalt are nil. He is 3-2 with a 2.16 ERA in five starts for Tulsa, and he pitched 8 1/3 innings of shutout ball in his last start, a 1-0 victory over Arkansas.
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.