HOUSTON—The first-round NBA playoff series between the Houston Rockets and Oklahoma City Thunder—and James Harden and Russell Westbrook—was supposed to be a showdown of the game’s most sublime guards. It was seized instead on Sunday by the game’s most irritating guard.

It would be a nightmare for almost everybody in the NBA to be stuck guarding Westbrook for an entire postseason series. It’s a dream for Patrick Beverley. This is a matchup of a player who hates to be annoyed and a player who loves to be annoying—and the proud...