There is possibly even a chance for a game six return. Here's a quote from Smart from the press conference before game 1:
"We're optimistic, but we're not going to rush anything," Smart said. "We're going to take it slow. So I think I have another doctor's appointment, checkup, in the next two weeks. We'll see what she says. If she clears us to be able to start a little bit earlier, than we might. But as of right now, Game 7 (or the) second round is the (goal)."
Game 6 is scheduled for April 26, if he is cleared 'a little bit earlier' then he might be available for that, assuming the series goes that long.