Weiss said he doesn't know who the Rockies will pick to make the start. A possibility is Colorado Springs righty Pedro Hernandez, who has 15 Major League appearances, including 13 starts, with the White Sox (2012) and Twins ('13).
With the Rockies off on Thursday, they also have the option to skip the fifth-starter slot and put off the decision until June 25, at home against the Cardinals. However, the current rotation includes two recent callups in their first Major League experience (righty Christian Bergman and lefty Tyler Matzek), and two players with injury concerns (righty Jhoulys Chacin missed the first month with a right shoulder strain and lefty Jorge De La Rosa is dealing with periodic back stiffness and a bruised left middle finger).
Thursday's off-day is the Rockies' last until July 10, so there are no other opportunities for extra rest on the horizon.
Thomas Harding is a reporter for MLB.com. Follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.