SEATTLE -- Marco Gonzales toed the emotional line between relief and frustration when revealing on Sunday that he’ll undergo season-ending surgery to address the nerve issue that’s been lingering for more than two months in his pitching forearm.

The left-handed veteran had long been looking for answers relating to the injury that’s sidelined him since his May 28 start against the Pirates, when he first experienced the most pronounced symptoms. Now Gonzales has clarity -- but it comes with an unfortunate conclusion to his 2023 season.

“There's this ticking clock of, ‘I need to come back this year’ and just trying to do everything I can,” Gonzales said. “And it's frustrating when you're not making any progress and you're seeing the team out there and you want to contribute, and I'm sitting here with still no answers and not making any progress. So I'm thankful that we've come to a diagnosis and a treatment plan.”

Specifically, Gonzales will undergo a “cleanout” to decompress the anterior interosseous nerve, which controls motor function for pronating the wrist and index finger.

The procedure will be performed on Aug. 22 by Dr. Steven Shin, the director of hand surgery at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles, who also repaired the UCL in Cal Raleigh’s thumb last offseason.

Gonzales estimated that by doing this now, he’ll be able to go through a regular offseason throwing program and be ready when pitchers and catchers report in Arizona in February.

“It's unfortunate news, and obviously, I wanted to avoid surgery at all costs,” Gonzales said. “But this is necessary, we believe, to right the problem.”

While this syndrome is “somewhat rare” in baseball, Gonzales said, it’s not a complete outlier. The lefty consulted other pitchers that underwent the procedure -- also by Dr. Shin -- such as the Giants’ Scott Alexander and former Mariner Brandon Morrow.

Alexander had the surgery midway through 2019 and returned by the start of the COVID-shortened ‘20 season, while Morrow underwent the procedure in ‘13 and returned to pitch for five more years.

“They've given me great advice to move forward with it, to get it cleaned out, because it's really worked for them. ... Thankfully, it's not a ligament or tendon or anything that needs to be repaired,” said Gonzales, who underwent Tommy John surgery as a member of the Cardinals in April 2016.

Gonzales, who was transferred to the 60-day IL on July 26, wasn’t sure if the issue first surfaced in his final 2023 start or if it was something slowly building. He described it as becoming “harder and harder to get loose each inning,” that he experienced “achy soreness” in his forearm and “basically ever since then, each time I go to throw a baseball, I feel this aching, sore pain in the middle of my forearm.”

Gonzales wound up pitching 5 2/3 innings on May 28, leading the Mariners to a win. Overall, Seattle went 7-3 in his starts this year, over which he compiled a 5.22 ERA with 34 strikeouts, 18 walks and a 1.46 WHIP in 50 innings.

Gonzales joins Robbie Ray among Mariners starters to undergo season-ending surgery this year. Ray had left flexor tendon and Tommy John surgeries on May 3, and he isn’t expected back until well into the 2024 season.

In their stead, Seattle has installed rookies Bryce Miller and Bryan Woo, who has since suffered minor forearm inflammation and went on the 15-day injured list on Aug. 5. Top pitching prospect Emerson Hancock then assumed Woo’s spot and looked promising in his debut.

Though the Mariners’ rotation has stayed afloat and been the primary catalyst for the club remaining in postseason contention despite an inconsistent offense in the first half, there’s no doubt that they’ve missed the innings accumulation from Ray and Gonzales, two workhorses with no workload limitations.

Manager Scott Servais said earlier Sunday that the club will need to get more creative to spread the workloads of their rookie starters down the stretch -- especially if they’re pitching into October.