Right-hander Jonathan Hernández underwent Tommy John surgery, Rangers president of baseball operations Jon Daniels confirmed during a pregame media conference Monday.

Daniels said that Hernández had the procedure Monday and that it went as expected.

Hernández will miss the entire 2021 season and is also expected to miss the beginning of ‘22.

Hernández was sidelined early in Spring Training with a low-grade UCL strain and was originally shut down for four weeks. After he underwent an MRI last week, Hernández’s injury showed some healing, but the right-hander felt discomfort.

Hernández opted to go through with surgery following the reevaluation, Daniels said.

“The decision was made rather than to invest more time in the rehab side, since [Hernández] was still having symptoms to go ahead and have the surgery,” Daniels said. “[Hernández] made that call towards the end of last week and had the surgery today.

Hernández was expected to be a key part of the Rangers’ bullpen in 2021. He was solid last season for Texas, posting a 2.90 ERA in 31 innings. He was sidelined early in Spring Training with a low-grade UCL strain on March 9.

The 24 year old has posted a 7-2 record with a 3.40 ERA in 47 2/3 innings through two big league seasons with the Rangers.

Losing Hernández for the year is a tough loss for a bullpen that has already had its share of injuries to start the year.

Matt Bush was recently sidelined with a flexor strain in his right arm and will be reevaluated in six weeks. Joely Rodríguez, who was sidelined during Spring Training with an ankle injury, will begin throwing in games at the club’s alternate site in Round Rock, Texas, as a part of his rehab.

Rangers manager Chris Woodward said he is looking for the younger bullpen arms to fill those gaps left by the injuries.

“I think we’re gonna have to try with certain guys and put guys in different spots,” he said. “It’s gonna put these guys in some tough spots, and [we’ll] see what they got.”

• Left fielder/designated hitter Khris Davis (quad) is around two weeks away from being cleared to play in games and will continue to get game ready before joining the big league club.

• Utility player Brock Holt (hamstring) is “feeling a lot better,” Daniels said. The hope is for Holt to be ready before his 10-day stint on the IL is over.

• Outfielder Willie Calhoun (groin) is getting work in at the alt site in Round Rock. He is undergoing intake testing as a part of MLB’s COVID-19 protocols and should be cleared to continue his rehab work within the next two days. Daniels said Calhoun is healthy and saw game action in Arizona before going to Round Rock.

• Top prospect and former first-round pick Josh Jung (foot) is starting to walk with a boot and is able to put weight on his left foot following surgery he had on it this past March.

• Catcher Sam Huff (hamstring) continues to get in work in Arizona and is expected to be ready to start the Minor League season by the end of the month.