The knuckleball has never been a popular pitch by any means (fewer than 100 MLB pitchers have used it as their primary pitch, per FanGraphs), but did you ever think it'd go extinct?
By the numbers: Just 727 knuckleballs were thrown in the majors last season, the fewest in the pitch-tracking era (2008-present). And since the guy who threw 719 of them, Boston's Steven Wright, has been limited to just six innings this year, we're on track for another record low.