Red Sox prospect Bryan Mata is out indefinitely with a slight tear of his ulnar collateral ligament. John Bazemore/Associated Press

The Red Sox are losing their top pitching prospect for at least the start of the season, if not longer.

Right-hander Bryan Mata, 21, has a slight tear in his ulnar collateral ligament and will be shut down indefinitely.

Mata experienced tricep soreness this week, but the Red Sox thought it was nothing serious until an MRI revealed the UCL damage.

Mata will not have surgery and instead will try to heal with rest and rehab.

“The doctors and physicians feel like it’s small enough so with treatment and doing that, he should be fine,” Manager Alex Cora said. “Obviously it’s going to take some time. There is no timetable.”

With a fastball that sits in the high 90s and developing off-speed pitches, Mata has climbed through the ranks quickly in the minor leagues, reaching Double-A as a 20-year-old in 2019. He was invited to big league camp and given a chance to impress this spring.

“If he is disciplined and follows everything that we are set to do, the hope is for him to come back,” Cora said. “He is very important to us. It’s a tough one.”

Cora stressed patience was the key for Mata in his recovery, but noted that anytime the UCL is involved, it’s scary.

“He’s young enough where probably everything is going fast for him right now,” Cora said. “But he is mature enough to understand these things happen over the course of your career. He did an amazing job in the offseason to get in shape and get his arm where it’s supposed to be. It’s an obstacle in his career, but we do feel he is going to bounce back and he is going to be OK.”

OUTFIELDER FRANCHY CORDERO made it to Red Sox camp for the first time on Saturday morning. He was a late arrival after dealing with COVID-19-related issues following the trade from the Kansas City Royals for Andrew Benintendi. Cordero will likely appear in his first Grapefruit League game soon.

“He’s a little bit behind physically,” Cora said. “But with the kind of athlete he is and his physicality… he should be able to catch up fairly quickly.

“We have to communicate with the player and make sure he understands he doesn’t have to rush. Whenever he’s ready, he’s ready. We still have plenty of time in terms of at-bats.”

RYAN WEBER started for the Red Sox against the Twins on Saturday and pitched two innings, allowing two runs. The game was called after two innings because of rain.