The way I see it, you shouldn't be doing the gig if you aren't willing to rehearse, especially with a band you've never played with. Sure, you can wing it, maybe even very well, but is it really worth the risk? Surely it's sensible, if nothing else, to get to grips with the drummer so you can lock in with him properly. Personally, if I asked someone to sub, it'd be on the condition that they came to at least one rehearsal, and it was to a good standard. However good you are, not rehearsing when you have a chance to do so is a terrible idea, and just asking for trouble. I'd also question the "I'm too good to need to rehearse with you" attitude.
Just my two cents, whatever works for you...