"We want to get him calmed down before we get him back started," manager Don Mattingly said. "We've got plenty of time."
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Locke initially felt something while throwing off the mound, and he was told to stop. The discomfort is more in the shoulder area of his biceps than near the elbow.
"With it being early, take the precautions you can take," Locke said. "Donnie said it best in the meetings. If any little thing is [acting] up, let's not make it a big thing by not taking care of it. We're trying to do the smart thing here, take a few days."
Locke signed as a free agent with Miami in December after being with Pittsburgh from 2011-16. Though he's in the mix for a rotation spot, he may wind up opening the season in long relief.
"Locke came up a little tender in his throwing program, so we stopped him a couple of days," Mattingly said. "Just hope to make sure we stay on top of it. They're calling it biceps tendinitis."
Locke was 9-8 with a 5.44 ERA in 127 1/3 innings with the Pirates in 2016. The Marlins are hopeful the lefty can start throwing later in the week.
"It was a three-day shutdown," Mattingly said. "He's able to do everything else. He will do the bunting, the PFPs, and do pretty much everything but [throwing]."
The medical staff is confident Locke isn't dealing with anything serious.
"I'm assuming it's not, until I hear otherwise," Locke said. "I think we'll take a couple of more days and try it out. If it feels good, we're back on the horse. If it doesn't, we'll take the next step."
• Giancarlo Stanton is sporting a new faceguard on his helmet, and the slugger used it during live batting practice on Monday. The guard is basically a flap that covers the left side of his jaw, and it's less obstructive to the wire attachment he had previously used.
"It's kind of easier to keep up with," Stanton said. "The bar would vary in distance from my face. If the helmet falls or anything, it moves and alters more than the helmet version."
Stanton was struck on the left side by a pitch on Sept. 11, 2014, at Milwaukee, and he missed the remainder of the season. He began wearing the football-helmet-style guard the following season.