Does DraftKings pay out if a tennis player retires?
Yes, once a full set is complete - the bet stands and settles on the player who advances, so backing the retiring player loses rather than being refunded. Before that set finishes, the stake is returned.
Does DraftKings settle a tennis disqualification like a retirement?
Yes, on the same one-set basis: after a completed set the player who advances wins, and before it the market is voided.
Are DraftKings tennis rules different for WTA matches?
Possibly. The one-set threshold is the ATP rule, and there are reports of a full-match requirement on the WTA side, which would mean a third-set retirement is refunded rather than settled. We cannot confirm it, so treat a women's match as the one to check.