Athletics righty Daulton Jefferies diagnosed with thoracic outlet syndrome

The A’s placed right-hander Daulton Jefferies on the injured list on Friday amid a series of roster moves, also optioning lefty Kirby Snead and recalling righty Jake Lemoine and left-hander Zach Logue. The A’s originally stated that Jefferies had some nerve irritation in his right arm, but manager Mark Kotsay now gives reporters a much more ominous update, revealing that the 26-year-old righty has been diagnosed with thoracic outlet syndrome via Matt Kawahara of the San Francisco Chronicle. He’s receiving a second opinion.

While not as common as Tommy John surgery, thoracic outlet syndrome often requires surgical repair — an operation that involves removing a portion of the player’s rib in order to alleviate nerve pressure. The success rate for pitchers returning from TOS hasn’t been as strong as those returning from the more common Tommy John surgery, though there are plenty of examples of hurlers who’ve returned to have successful careers. Arizona’s Merrill Kelly, for instance, had thoracic outlet surgery in September, 2020 and was back on the mound for a slate of 27 starts in 2021. He’s made another eight starts of 3.27 ERA ball this season.

It’s yet to be seen whether Jefferies will undergo surgery, which would likely end his season. That’ll surely hinge on what he and the A’s hear in his forthcoming second opinion. Even in the event of a non-surgical route, an absence of some note seems safe to expect.

Selected by the A’s with the No. 37 overall pick back in 2016, Jefferies entered the year with just 17 big league innings under his belt. However, the Athletics’ offseason fire sale shipped both Chris Bassitt and Sean Manaea to other clubs, opening the door for Jefferies to win a long-term spot on the starting staff. Jefferies posted a 1.17 ERA through three starts but has been rocked for 23 runs over 24 innings in his past five turns. Overall, he carries a 5.72 ERA with a 16.3% strikeout rate, a 4.7% walk rate and a 46.6% grounder rate. Metrics like fielding independent pitching (3.76) and SIERA (4.15) feel he’s been a good bit better than his ERA would indicate.

The A’s still control Jefferies for five seasons beyond the current campaign, so even if he doesn’t factor into the mix again this season, he should have ample opportunity down the road. For the time being, with Jefferies sidelined, Oakland will look to Frankie Montas, James Kaprielian, Paul Blackburn and a returning Cole Irvin, who’s slated to come off the injured list and start a game this weekend. Logue, recalled Friday, will probably step directly into the rotation. One of four players acquired in the trade that sent Matt Chapman to Toronto, he’s already made four appearances (three starts) and pitched to a 2.04 ERA with an 18.9% strikeout rate against a 6.8% walk rate in 17 2/3 frames.

Should the A’s need another starter in the near future, they have a pair of other newly acquired options to evaluate. Right-hander Adrian Martinez, acquired from the Padres in the Manaea trade, made his big league debut in a doubleheader against the Tigers last week and tossed 5 1/3 shutout innings with three strikeouts and no walks. Fellow right-hander and trade acquisition Adam Oller, who came over from the Mets as part of the return for Bassitt, could be an option as well. He’s already made four big league starts with the A’s, though he’s been tagged for 20 runs in 14 2/3 frames.