The rookie backstop began the day batting .229 (8-for-35) with one home run and five RBIs in 11 games since the All-Star break.
Manager Manny Acta's decision to sit Santana opposite CC Sabathia was hardly surprising. The switch-hitting Santana has a .143 average in 42 at-bats against left-handed pitching this season.
"The way things have gone, this would be the time to give him a day off," Acta said.
Chris Gimenez started behind the plate in place of the 24-year-old Santana, whose batting average (.269) has dipped below .270 for the first time since June 16, his fifth big league game.
"He's battling, but he's being pitched tough right now," Acta said. "He's like everybody else. He's going to get down, and then he's going to get right back up again. He just needs to be patient.
"He'll be all right. Things are not always going to be rosy for him."