Highly-regarded Miami Marlins left-hander Robby Snelling was placed on the 15-day injured list Wednesday with a UCL sprain in his pitching elbow.

The severity of the injury hasn't yet been determined but Snelling is unlikely to return soon. If Tommy John surgery is deemed necessary, he would miss the rest of this season and possibly most of the 2027 season.

Marlins manager Clayton McCullough said Snelling will undergo further testing. Snelling had been scheduled to start Thursday's road game against the Minnesota Twins.

The news comes just five days after Snelling made his major league debut against the Washington Nationals. Snelling, 22, is rated as the organization's No. 2 prospect by MLB Pipeline.

"Robby was certainly disappointed," McCullough told reporters prior to Wednesday's game against the Twins. "You know, you work your entire life for the opportunity to become a major league player, and you come up, and you make your major league debut, and then for something to pop up like this very shortly after, it's disappointing."

Snelling (0-1) gave up three runs and five in five innings in a 3-2 loss to Washington. He walked four and struck out two.

But his arm didn't bounce back as start No. 2 neared.

"Robby reported some discomfort (Tuesday) following his bullpen session," McCullough said. "There will be some further evaluations and things to occur. We don't have anything more on the time frame."

Left-hander Braxton Garrett will start in place of Snelling on Thursday. It will be his first start since big league start since June 2024 due to arm issues. He eventually underwent Tommy John surgery six months later.

Garrett, 28, was 0-2 with a 2.30 ERA in six starts for Triple-A Jacksonville. He is 16-19 with a 4.03 ERA in 65 appearances (63 starts) since reaching the majors with the Marlins in 2020.

Miami also activated right-hander Pete Fairbanks on Wednesday. The closer was on the 15-day IL due to nerve irritation in the hand.

Fairbanks, 32, is 0-2 with five saves this season. His ERA is 10.00.

Snelling joined the Miami organization in the July 2024 trade that sent relievers Tanner Scott and Bryan Hoeing to the San Diego Padres. The Marlins also received three other prospects in the deal.