halladay had one in the playoffs, so I do think playoff level teams can be completely shut down. Heck, Anibal and Max had nice ones going v. the Dodgers this year.
Roy Halladay had a perfect game during the regular season, on 29 May 2010 against the Marlins. His post-season one was a no-hitter in the NLDS, not a perfect game.
Don Larsen's perfect game is even more remarkable in that it was not a dominant pitcher against a weak lineup, but a journeyman pitcher who played for seven teams against a lineup with four future Hall-of-Famers (and non-HOFer Gil Hodges, who hit .304 in that World Series).
