Colorado manager Jim Tracy said the diagnosis was made by a doctor in St. Louis and that Chacin will not throw for the next few weeks.
"I think we've discovered what had some people saying, 'Well, he's dropped a couple miles per hour [in velocity],'" Tracy said. "What I'm encouraged by is that we don't have any issues structurally.
"We'll give this some time and see how it goes. I think with exercising, strengthening, things like that, we're going to be able to figure this out."