Carpenter has not thrown since March 3, when he began to experience neck stiffness while throwing live batting practice. The discomfort persisted, prompting Carpenter to undergo several exams, most recently on Friday, in an effort to determine the source of that pain.
That source, Mozeliak announced, is not nerve-related but rather due to a bulging disc in Carpenter's neck. Mozeliak said that Carpenter has been dealing with a bulging disc for a few years. Carpenter was not available to provide additional background about the issue or prognosis. The veteran right-hander said, through a spokesperson, that he would wait until Monday to address reporters.
Mozeliak said that the organization will wait a few days before determining when Carpenter might be able to return to the mound. Carpenter has indicated feeling improvement in recent days and continues to undergo treatment. The Cardinals are hopeful that, even if not corrected, the bulging disc can be managed.
"Right now, he is progressing so the way we're looking at it is it's very positive," Mozeliak said. "... We're encouraged with where he's at. Obviously, the next big test will be when he goes out and throws."
The Cardinals are not yet ready to rule Carpenter out as their Opening Day starter. However, with less than four weeks left before the start of the regular season, Carpenter would need to get back on the mound soon in order to be have ample time to get ready.
Mozeliak said that Carpenter would likely need three spring starts in order to begin the season on time. Carpenter made just three Grapefruit League appearances last year.
Preparations are beginning to be made, though, in case Carpenter isn't ready to go in early April. Mozeliak said that the club has plans to begin stretching another pitcher out this week. He did not identify who that pitcher would be, noting that he wanted to first make sure that the individual has been notified of the organization's new plans.
Four of St. Louis' projected relievers -- Lance Lynn, Marc Rzepczynski, Kyle McClellan and Mitchell Boggs -- all have extensive experience starting. Lynn has already made a multi-inning appearance this spring. There's a chance, too, that the Cardinals could otherwise look to one of their Minor League starters, such as Brandon Dickson or even Shelby Miller, if they don't want to mess with the makeup of the bullpen.
Right now, the Cardinals still need a starter for Wednesday's Grapefruit League game against the Astros. The club could use that spot for whomever they have designated as this Plan B.
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.