Someone can correct me, but I think Ashby was up as an extra spot that MLB allows for doubleheaders. If Curtiss goes on the IL, that gets you back to the non-doubleheader roster limit. So, if they're bringing up Lindblom, someone else has to go down. This is the last series at Wrigley this season, so if they had to postpone tonight, they would probably try to do a doubleheader tomorrow (so, back to doubleheader roster size). The next series for the Brewers is at Pittsburgh, which isn't that long a flight, so another game tomorrow, while not ideal, isn't that much of a killer travel-wise.