The discomfort has been there since Spring Training, A's manager Bob Melvin said, but it wasn't until Sogard was playing in a rehab game with Class-A Advanced Stockton on Wednesday -- his second rehab game -- that it become a significant issue again.
"It's popped up enough to where it's worrisome," Melvin said. "To go and get an MRI yesterday means we're concerned about it."
• The A's tweaked their rotation to ensure ace Sonny Gray pitches on normal four days' rest on Saturday against the Royals, pushing righty Chris Bassitt to Sunday. Following Monday's off-day, the rotation will line up like this for a three-game series in New York: Eric Surkamp, Kendall Graveman and Rich Hill.