Floyd will undergo the MRI on Thursday afternoon in San Diego.
"From that point, we'll move forward with a plan," Padres manager Bud Black said. "It's been a nagging thing."
Floyd originally went on the disabled list with a strained right shoulder. He began taking batting practice while the Padres were in New York and Philadelphia and was ready to start a rehab assignment Monday before tweaking his knee Saturday.
"He said there was nothing he could point to that caused the swelling," Black said. "We have to get him on the field. The shoulder seems to be under control, so we'll just continue to try and get through this."
In related news, right-hander Cha Seung Baek came out of his bullpen session Tuesday in good shape and will throw another "high intensity" bullpen Friday and if all goes well, "you could possibly see him on a Minor League assignment by Monday," Black said.
Rick Eymer is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.