SAN FRANCISCO -- Buster Posey was a late scratch from the Giants' lineup for Sunday's series finale against the Orioles because of lower back tightness. He pinch-hit in the ninth inning of the 8-7 loss, drawing a walk and leaving for a pinch-runner. He is considered day to day.
"It's been a little stiff, it might've been from the travel," said manager Bruce Bochy. "It's been there for a couple days, it was at a point where we felt it was best to give him a day."
Trevor Brown started at catcher in Posey's absence, and Hunter Pence assumed the cleanup spot in the batting order. 
Before the Posey annoucement, the Giants appeared to have their healthiest 25-man roster since Opening Day. The only players on the disabled list are relief pitchers Cory Gearrin and Josh Osich and outfielder Mac Williamson. And they could be returning to the club soon.
‬Williamson, who went on the DL on Aug. 2 because of a left shoulder strain, began a rehab assignment Sunday with Triple-A Sacramento. The outfielder was batting .245 with 15 RBIs and six home runs before he was injured in San Francisco's game against the Nationals on July 31.
‬Gearrin, who was placed on the 15-day DL on July 6 (shoulder strain), is nearing a full recovery as well, and Bochy said the Giants would make a decision regarding his return soon.
‬Gearrin has appeared in seven games for Sacramento, allowing just one run on four hits in seven innings.
‬"He's throwing the ball well down there," said Bochy. "We have to figure out what we're going to do."
Worth noting
Bochy mentioned after the Giants' 6-2 win over the Orioles on Saturday that players like Pence and Joe Panik, who recently came of the DL, have experienced struggles at the plate because they're still in "rehab mode."
Panik broke out of his slump on Saturday, going for 3-for-3 with a walk. But Pence has continued to struggle since rejoining the club on July 30. He entered Sunday's series finale 9-for-51 (.176) since being activated.