Posey day to day with nerve irritation in back

DENVER -- Giants catcher Buster Posey went on day-to-day playing status Tuesday with nerve irritation in his lower back.

The ailment prevented Posey from starting the opener of a challenging three-game series against the Colorado Rockies. The National League West-leading Giants entered the series leading Colorado by three games. Center fielder Angel Pagan (left shoulder) also was out of the lineup, forcing the Giants to confront the Rockies without two of their top offensive performers.

Posey, the 2012 NL Most Valuable Player and two-time All-Star, said that he probably will be sidelined for a couple of days "if I had to guess."

"Buster needs a day [off]," manager Bruce Bochy said. "He might need a couple. We'll see how he feels tomorrow."

Posey, 27, said that he hurt himself while taking a "funky swing" as he struck out in the seventh inning of the Giants' 4-1 victory Sunday against Miami. Though he suspected nothing amiss at the time, Posey said that his back stiffened after the game and during Monday's scheduled off-day.

"I really don't think it's anything super serious," said Posey, who said that he'd be available to pinch-hit if necessary.

Posey started 38 of San Francisco's first 45 games, including 33 at catcher and five at first base. He's batting .278 with seven home runs, 23 RBIs and an .813 OPS (on-base plus slugging percentage).