What do they mean when they say that the Kentucky Derby might be run on an off-track?

Question

What do they mean when they say that the Kentucky Derby might be run on an off-track?

Answer 1

The term 'off-track' is used to designate a surface which is not "fast" which is the usual condition. It is raining in Kentucky right now, so the 'experts' are predicting that the official track condition will be listed as "good" or "muddy" or "sloppy" or "Heavy", general designations that are designed to show how much moisture the track is holding.

Answer 2

That it might rain tomorrow.  An off track in horse racing just means that the track is wet.  Obviously, rain would skew race and how some horses perform.