SAN FRANCISCO -- Rays ace Shane McClanahan will undergo Tommy John surgery next Monday, manager Kevin Cash said before the team's game against the Giants on Tuesday. He is expected to miss the entire 2024 season.

The Rays got multiple opinions on McClanahan's injury before determining the best course of action. After McClanahan was evaluated by Dr. Keith Meister in Texas on Tuesday, the club decided that Tommy John surgery would give the 26-year-old left-hander his best chance at coming back strong.

One of the best pitchers in the Majors the first half of the season, McClanahan was sidelined from late June until after the All-Star break by mid-back tightness. He struggled in his return, allowing 15 runs in 19 innings over four starts, then noted tightness in his left forearm during the final inning of his Aug. 2 outing at Yankee Stadium.

A day later, McClanahan was placed on the 15-day injured list and evaluated by orthopedic team physician Dr. Koco Eaton. He received a second opinion from Dr. Neal ElAttrache a few days later. At that point, Cash acknowledged it was “highly unlikely” that McClanahan would return this season. The Rays made that official on Saturday by transferring the All-Star to the 60-day IL.

Now, McClanahan likely will not pitch for the Rays until 2025.

"Tough loss, no doubt," Cash said.

It will be McClanahan's second Tommy John surgery. He missed his first season at the University of South Florida while recovering from the procedure in 2016. The typical recovery period is 12-14 months, but the timeline becomes less certain for players who have had the operation twice.

It’s another huge blow to the Rays’ rotation, which never got a full turn from their top five starters heading into the season: McClanahan, Tyler Glasnow, Jeffrey Springs, Drew Rasmussen and Zach Eflin.

Glasnow missed the first two months of the season with a strained oblique, and he missed his last start due to back spasms. Springs had Tommy John surgery on April 24 and will be out until next season. Three months later, Rasmussen underwent a hybrid internal brace procedure that will sideline him until midseason next year.

Now, they know roughly how long they’ll be without McClanahan. And this might be their toughest loss yet, given McClanahan’s elite ability and standing in the clubhouse.

A two-time All-Star, the Rays’ Opening Day starter each of the past two seasons and their Game 1 starter in the postseason in 2021 and ’22, McClanahan began the season 11-2 with a 3.29 ERA and 121 strikeouts in 115 innings. Tampa Bay won 14 of his first 17 starts and 15 of 21 overall this year. McClanahan memorably made his Major League debut as a reliever in the 2020 postseason. Over the last three years, he’s put together a 33-16 record and 3.02 ERA with 456 strikeouts in 404 2/3 innings across 74 starts.

The Rays are expected to use a four-man starting rotation as often as possible the rest of this month, leaning heavily on Glasnow, Eflin, Trade Deadline acquisition Aaron Civale and converted reliever Zack Littell. Rookie Taj Bradley could round out the rotation in September, if not sooner.

Before a stretch of 17 games in 17 days starting Sept. 1, the Rays should have little need of a fifth starter. When they do, they will likely mix and match with their bullpen (including multi-inning reliever Erasmo Ramírez) and a handful of bulk-inning arms bouncing between Triple-A and the Majors, including Josh Fleming, Cooper Criswell, Jalen Beeks and prospect Jacob Lopez, who debuted Monday night.