"We're just being cautious with it," said Phillies assistant general manager Scott Proefrock. "(Brian) Schneider will catch and it's a day to day thing."
Proefrock said he believes Ruiz injured himself during Sunday's 8-3 loss to the St. Louis Cardinals.
"He stayed in (the game) and we took look this morning and decided to take him out of the lineup and give him another day off," Proefrock said.
With Ruiz out of the lineup, Shane Victorino will take over as the cleanup hitter. Schneider, Ruiz's fill-in behind the plate, will bat eighth behind second baseman Freddy Galvis.