Dave Roberts of the Giants became, I believe, the fifthsixth seventh player to reach first on catcher's interference this year. Roberts was awarded first by home plate umpire Chuck Meriwether in the second inning at Arizona tonight. Miguel Montero was the guilty party and it was the second time he was called for it this year. Montero earlier was called for catcher's interference against Andre Ethier of the Dodgers.
So far, I have the following instances of catcher's interference:
April 4: Edwin Encarnacion of the Reds batting, Michael Barrett of the Cubs catching. (thanks to Tom.)
April 15: Rafael Furcal of the Dodgers batting, Rob Bowen of San Diego catching
April 16: Andre Ethier of the Dodgers batting, Miguel Montero of Arizona catching
April 24: Darin Erstad of the White Sox batting, John Buck of Kansas City catching
April 25: Miguel Tejada of Baltimore batting, Jason Varitek of Boston catching
April 27: Eric Byrnes of Arizona batting, Rob Bowen of San Diego catching (thanks to benberg09)
April 28: Dave Roberts of San Franciso batting, Miguel Montero of Arizona catching.
Erstad has reached on catcher's interference 12 times, Roberts did it for the second time (he got one last year against Yadier Molina of St. Louis). Byrnes, then of Oakland, had reached previously in 2003 against Einar Diaz of Texas. Encarnacion led the NL with four CIs last year. Furcal, Ethier, and Tejada were newcomers to this aspect of baseball's miscellany.