Saunders has appeared in just nine games this season because of ongoing issues with his knee. He tore the meniscus during Spring Training and then underwent a surgical procedure to have 60 percent of it removed from his knee.
The 28-year-old returned in late April but wasn't himself on the field. He was later diagnosed with a bone bruise, and he'll likely need another couple of weeks before he can start load-bearing exercises, which would then eventually lead into a rehab assignment.
"This isn't necessarily common, but it has happened before, and the annoying thing with the bruise is you've just got to rest it, otherwise it will come back and it will never go away," said Saunders, who was acquired during the offseason in a trade with the Mariners for left-hander J.