JUPITER, Fla. -- New York Yankees manager Aaron Boone said reliever Tommy Kahnle is "a little behind" as he builds up strength following a shoulder injury and could start the season on the injured list.

"We'll see," Boone said when asked if Kahnle will be ready for Opening Day. "I think he'll be ready, but it's a matter of do we want him to have more games under his belt? That's what we're kind of deciding."

Kahnle, 34, was one of the Yankees' best relievers in 2023 when healthy. But injuries hindered his return to the Bronx after signing a two-year, $11.5 million contract and appearing in just 14 games over the previous three seasons.

The right-hander missed the first two months of the 2023 season with right biceps tendinitis before returning to post a 2.66 ERA in 42 relief appearances. He was then placed on the injured list in late September with right shoulder inflammation to end his campaign.

While Kahnle has yet to appear in a Grapefruit League game this year, Boone said he has been throwing bullpen sessions.

"He probably won't be in a game until more towards the end of spring," Boone said.

Kahnle, who spent parts of four seasons with the Yankees through 2020, is projected to serve as one of the Yankees' two primary setup men -- in tandem with fellow right-hander Jonathan Loaisiga -- for closer Clay Holmes.

Ian Hamilton, Ron Marinaccio, Scott Effross, Nick Burdi and Luke Weaver are among the other right-handed options for the bullpen.