SAN FRANCISCO -- A week with a couple of off days was setting Buster Posey up to potentially start four straight games for the first time this year, but Posey was pulled from the Giants' lineup against the Athletics before he could extend that run to three starts.
The Giants scratched Posey about 90 minutes before the first pitch Friday because of lower back tightness. Curt Casali was inserted in the seventh spot of the lineup for the opener with the A's.
The tightness takes a key right-handed bat out of the lineup against A's lefty Sean Manaea, who enters with a 3.01 ERA. Posey is batting .382 against left-handed pitching this season with a 1.088 OPS.
The Giants have been extremely careful with Posey's playing time this season, one reason why he's having one of the best offensive seasons of his career. He started both games in Anaheim, and with the off day Thursday it seemed the Giants could start him the first two games of this series, rest him Sunday, and then start him twice against the Los Angeles Dodgers early next week. That's now on hold.
The Giants also are without Brandon Belt, who was placed on the IL earlier Friday with right knee inflammation.