Kershaw took a painful step going to first base Monday night, and Mattingly said it's "a little plantar fasciitis. He took a funny step and just felt it."
Mattingly said Kershaw has been receiving treatment for the condition for "at least a week."
"He says he doesn't feel it at all [while pitching, only when running]. They're trying different tape and things at night to help it go away," Mattingly said.
Kershaw allowed three runs in a seven-inning no-decision Monday night against the Phillies.