If it rains
This appears to be a problem for pure epistemic accounts of indicative conditionals (a la Weatherson and Chalmers), on which "if A then B" is true iff the [epistemically] closest worlds verifying A also verify B.
The match cannot be played if it rains; either it has to be postponed or canceled. Which of these will happen is regulated by the rule book, but nobody has looked up the relevant passages so far. All we know is that exactly one of these two conditionals is in the rule book, and therefore true, and the other false:
1) if it rains, the match will be postponed.
2) if it rains, the match will be canceled.
Going to the epistemically closest worlds where it rains, I find some where the match is postponed and others where it is canceled. So both conditionals come out either false or indeterminate. But we want one of them to be true and the other false. (And we want their disjunction to be true, but one could possibly get that by tinkering with "or".)
Update: Here's a version for impure epistemic accounts a la Nolan.
Same setting as before, except that we also truly believe (from different sources) that a) it won't rain, and that b) the match will not be canceled. To evaluate "if it rains, the match will be canceled", we should now look at the world w such that i) it rains at w, ii) those of our actually true beliefs compatible with (i) are also true at w, and iii) among the worlds satifying (i) and (ii), w is closest to the actual world by the similarity standards for counterfactuals. Since we truly believe that the match will not be canceled, (ii) will presumably rule out all worlds where it rains and the match will be canceled. So on this account, "if it rains, the match will be canceled" is false. But in fact, it may well be true, if that's what the rule book says.
The background worry here is that conditionals can be true independent of what anyone believes or knows; so any analysis that builds doxastic or epistemic clauses into the truth conditions seems wrong. Suppose it is a law of nature that if it rains the match will be canceled (or take a suitable other example). What does this law say? Does it say that the epistemically closest worlds where it rains the match will be canceled? It seems not. The law doesn't make any claim about epistemic states.
The rule book which nobody has checked yet is reminiscent of the unopened ship's logbook that Hacking uses to argue that epistemic modals are sensitive to more than the actual knowledge of the members of a relevant group, suggesting some notion of "available evidence". What's true for epistemic modals should of course also be true of epistemic conditionals if they exist. In the case of epistemic modals, this is rather extensively discussed on the literature: Hacking, I. (1967). "Possibility," Philosophical Review 76: 143-168. Teller, P. (1972). "Epistemic possibility," Philosophia 2: 203-320. DeRose, K. (1991). "Epistemic possibilities," Philosophical Review 100: 581-605.