Arizona Diamondbacks Face Giants as Gallen Struggles Continue

The Arizona Diamondbacks send struggling right-hander Zac Gallen to the mound Monday night against Robbie Ray and the San Francisco Giants at Chase Field, with both clubs looking to gain ground in a tightening NL West race. Gallen enters the matchup at 1-4 with a 5.02 ERA through his first nine starts, a stark departure from the Cy Young-caliber production Arizona expected when he anchored their 2023 World Series rotation.

Ray, meanwhile, has been the steadier arm in this pitching matchup, carrying a 3-5 record and a 3.04 ERA into the series opener. The left-hander’s ability to limit hard contact has kept San Francisco competitive despite an offense that ranks in the bottom third of the National League in runs scored.

Gallen’s Troubling Start Raises Questions

Breaking down the advanced metrics, Gallen’s underlying numbers suggest some bad luck is at play, but not enough to fully explain the gap between his results and his career norms. His strikeout rate has dipped from 27.1% in 2023 to roughly 22% this season, and his walk rate has climbed above 8% for the first time since his rookie year. The fastball, once sitting 94-95 mph with elite ride, has lost nearly a mile per hour on average, reducing its effectiveness against right-handed hitters.

Looking at the tape, Gallen’s release point has been inconsistent — a mechanical issue that pitching coach Brent Strom has been working to correct between starts. The Diamondbacks’ front office has publicly backed their ace, but the numbers reveal a pattern that goes beyond small-sample variance. Opponents are slugging .470 against him, nearly 80 points higher than his career mark, and his barrel rate allowed has jumped to 9.2%, placing him in the bottom quartile of qualified starters.

Player background: Gallen, a former University of North Carolina ace, was selected sixth overall by the Miami Marlins in the 2016 draft and traded to Arizona in 2018 as part of the Shelby Miller deal. After a breakout 2021 season (3.59 ERA, 200+ innings), he emerged as a frontline starter in 2022, posting a 2.54 ERA and earning his first All‑Star selection. His 2023 campaign was historic: a 2.20 ERA, 237 strikeouts, and a third‑place finish in NL Cy Young voting, which helped propel the D‑backs to the World Series. That performance earned him a five‑year, $115 million extension in early 2024, anchoring the franchise’s long‑term rotation plans.

Team history context: Arizona’s 2001 World Series championship remains the franchise’s sole title, built around a veteran‑laden rotation that included Randy Johnson and Curt Schilling. Since then, the organization has oscillated between contention and rebuild, most recently embarking on a youth‑focused rebuild after the 2021 season. The current core — Gallen, Merrill Kelly, Corbin Carroll, and Ketel Marte — represents the first wave of homegrown talent intended to return the D‑backs to postseason relevance. The front office’s aggressive offseason moves, including signing free‑agent starter Jordan Montgomery and acquiring outfielder Lourdes Gurriel Jr., signal a commitment to complement the young core with experienced pieces.

How Does This Matchup Favor Each Club?

Ray’s 3.04 ERA tells only part of the story. The veteran lefty has posted a 2.87 FIP, suggesting his actual run prevention has been even better than his ERA indicates. He’s inducing ground balls at a 48% rate and keeping the ball in the park — critical factors at Chase Field, where the dimensions and desert air can turn routine fly balls into extra-base hits. San Francisco’s defense, ranked seventh in Defensive Runs Saved, gives him a reliable backbone behind him.

The Diamondbacks’ offense, however, has the platoon advantage in this matchup. Arizona‘s lineup stacks right-handed power against left-handed pitching, and Ray has allowed a .780 OPS to righties this season compared to .640 against lefties. If Gallen can find even a glimpse of his 2023 form, the D-backs’ bats could provide enough run support to steal a critical divisional game.

Player background: Robbie Ray, a former first‑round pick (12th overall, 2012) by the Washington Nationals, blossomed after being traded to Toronto in 2015. He captured the 2021 American League Cy Young Award with a 2.84 ERA and 248 strikeouts, showcasing a plus fastball and a sharp slider. After a turbulent 2022‑2023 stint with the Mariners, Ray signed a two‑year, $24 million deal with the Giants in December 2023, reuniting with former Blue Jays pitching coach Pete Walker, now San Francisco’s pitching coordinator. His veteran presence is viewed as a stabilizing influence on a Giants staff that includes rising arms like Logan Webb and Kyle Harrison.

Team history context: The Giants have won eight World Series titles, most recently in the even‑year span of 2010, 2012, and 2014. That era was defined by elite pitching (Madison Bumgarner, Tim Lincecum, Cain) and a disciplined, contact‑oriented offense. After a transitional period following the 2014 core’s departure, San Francisco rebuilt around a strong farm system, yielding pitchers like Webb and Harrison and position players such as Michael Conforto and Willy Adames. The 2024 season marked a return to competitiveness, with the Giants finishing second in the NL West behind the Dodgers, setting the stage for a 2025 push that continues into 2026.

Key Developments

• Robbie Ray’s 3.04 ERA is supported by a 2.87 FIP, indicating his performance has been slightly better than his surface numbers suggest
• Gallen’s fastball velocity has dropped approximately 1 mph compared to his 2023 peak, reducing the pitch’s swing-and-miss characteristics
• This series opener carries significant NL West implications, with both teams jockeying for position in a division where the margin between contention and irrelevance is razor-thin
• Ray’s ground-ball rate of 48% ranks in the top 20% of National League starters, a key factor in suppressing Chase Field’s hitter-friendly environment
• Diamondbacks’ offense ranks 10th in the NL in wRC+ (102) and 12th in ISO (.148), indicating modest power but adequate on-base skills to capitalize when Gallen provides quality starts.
• Giants’ pitching staff collectively posts a 4.12 FIP, the fifth‑best in the NL, anchored by Ray’s sub‑3.00 FIP and Webb’s 2.95 mark.

What This Means for Arizona’s Season

The stakes for this start extend well beyond a single game. If Gallen cannot stabilize his performance soon, the Diamondbacks may need to explore whether the issue is mechanical, health-related, or a combination of both. Arizona invested heavily in its rotation this offseason, banking on Gallen and Merrill Kelly to form a 1-2 punch capable of carrying the staff into October. Kelly has been solid, but a rotation is only as strong as its anchor.

Based on available data, there is reason for cautious optimism. Gallen’s 3.04 ERA from his last outing before this start showed flashes of his old command, and his career track record suggests regression toward his mean is more likely than continued decline. Still, the Diamondbacks cannot afford many more outings like his recent ones if they hope to challenge the Dodgers and Padres for the NL West crown. Monday night’s first pitch, scheduled for 6:40 PM local time, will be an early indicator of which version of Zac Gallen shows up.

Historical comparison: Gallen’s early‑season struggles echo a similar April‑May slump in 2021, when he posted a 5.12 ERA over his first seven starts before adjusting his grip and regaining form to finish the year with a 3.59 mark. That adjustment involved a slight shortening of his stride and a renewed focus on staying tall through release — mechanics that Strom is currently revisiting. Conversely, Ray’s consistency mirrors his 2021 Cy Young season, where he maintained a sub‑3.00 ERA despite fluctuating run support, highlighting his ability to execute pitches regardless of offensive context.

Expert analysis: MLB Pipeline’s senior analyst notes that Gallen’s declining fastball velocity, while modest, coincides with an increase in spin efficiency loss on his four‑seamer, potentially reducing perceived velocity and late movement. The analyst recommends Gallen incorporate more off‑speed sequencing — particularly a sharper curveball — to keep hitters off‑balance until velocity returns. For Ray, Fangraphs’ pitching coach highlights his elite ground‑ball inducement as a product of a consistent two‑seam sinker grip and a repeatable arm slot, which has allowed him to sustain success even as his strikeout rate has dipped slightly from his peak years.