Diamondbacks Have a Pivotal Series Lying Ahead

A crucial divisional matchup is looming at Chase Field.

May 12, 2026; Arlington, Texas, USA; Arizona Diamondbacks pitcher Zac Gallen (23) throws against the Texas Rangers during the first inning at Globe Life Field. Mandatory Credit: Andrew Dieb-Imagn Images | Andrew Dieb-Imagn Images

The Arizona Diamondbacks return home to Chase Field to take on the San Francisco Giants for a three game series starting Monday night.

They finished off a 3-3 road trip to Texas and Colorado by defeating the Rockies 8-6 on Sunday. Coors Field was just the tonic for a struggling offense, as they scored 19 runs and batted .318 for the series. Corbin Carroll was the catalyst, going 5-for-12 with two homers and three walks in the series.

The D-backs are 22-23 and are hoping to get back over .500 playing against the division rival Giants who are 20-27. San Francisco are 6-4 in their last 10 games however, and are coming off a 10-1 victory over the Athletics.

Diamondbacks vs Giants Pitching Matchups

Monday May 18, 6:40 p.m. MST

Robbie Ray and Zac Gallen pitching stats | Jack Sommers

Robbie Ray is getting just 2.92 runs per game of support, hence his 3-5 record despite a solid 3.04 ERA. It's notable that expected metrics such as xERA (4.58) and FIP (4.92) are significantly higher than his ERA. Ray's 91.1% left-on-base rate is the second-highest in MLB.

Apr 18, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Zac Gallen (23) throws against the Toronto Blue Jays in the first inning at Chase Field. Mandatory Credit: Rick Scuteri-Imagn Images | Rick Scuteri-Imagn Images

Zac Gallen is a shell of his former self these days. He has an ERA over five, and he's earned it according to the advanced stats. He's not getting swing-and-miss on his fastball and not getting chase on his curveball. The former ace continues to search for answers after allowing seven runs, four earned in a loss to the Rangers on May 12.

Tuesday May 19, 6:40 p.m. MST

Landen Roupp and Ryne Nelson stats | Jack Sommers

Landen Roupp has a solid 3.49 ERA and has allowed just 35 hits in 49 innings, including two homers. His advanced stats are almost a run lower than his actual ERA. He's given up nine runs in his last 13.1 innings, so the D-backs might be catching him at the right time.

Not an especially hard thrower, Roupp has a 93.2 MPH sinker and also throws a curveball and changeup for swing-and-miss and weak contact.

Ryne Nelson has turned his season around after two horrific starts in late April drove his ERA up to 7.71. Since the calendar flipped to May, he's given up just five runs in 19.1 innings for a 2.33 ERA this month.

He's struck out 19 and walked three during this stretch. The team has not given him run support though, as the D-backs lost each of the three starts while scoring six runs total in those starts.

Wednesday, May 20 12:40 p.m. MST

Tyler Mahle and Merrill Kelly pitching stats | Jack Sommers

Tyler Mahle has either been lights out, giving up zero runs, or getting knocked around and allowing four or five runs lately. His ERA ballooned up to 5.59 after two rough starts most recently. The 31-year-old veteran has not faced the Diamondbacks since 2022.

Merrill Kelly is coming off his first ever complete game. He allowed one run in nine innings to the Rockies at Coors field on May 15. That came after allowing just one run in seven innings to the Mets on May 9. While his 5.91 stands alongside a 7.85 xERA and 5.92 FIP, Kelly clearly has turned a corner after an extremely poor start to his season in his first four starts.

Diamondbacks vs Giants Bullpens

May 17, 2026; Denver, Colorado, USA; Arizona Diamondbacks relief pitcher Paul Sewald (38) pitches in the ninth inning against the Colorado Rockies at Coors Field. Mandatory Credit: Isaiah J. Downing-Imagn Images | Isaiah J. Downing-Imagn Images

The Giants' 3.45 reliever ERA ranks ninth in MLB, although it always needs to be remember they pitch in one of the most pitcher friendly parks in the league.

The Giants optioned struggling closer Ryan Walker to Triple-A on May 10 and have since been spreading save Chances around between Caleb Killian (1.80 ERA), Matt Gage (1.40 ERA), and Erik Miller.

Paul Sewald rebounded from a blown save in Texas to lock down the Sunday victory in Colorado. He is 10-for-11 in save chances, but also has four losses and a 4.41 ERA.

Brandon Pfaadt was shaky again as the long man in that game and was charged with four runs while recording just one out. He has a 6.34 ERA, and his roster spot might be in jeopardy.

Juan Morillo (1.83 ERA), Ryan Thompson (3.00), Kevin Ginkel (3.50), Jonathan Loaisiga (3.12) and Taylor Clarke (2.18) have all been solid. Clarke has allowed six of 11 inherited runners to score however and might best be used to start a clean inning.