San Francisco Giants vs Arizona Diamondbacks Prediction, Odds and Picks for Today, 05/18/26

The Giants and Diamondbacks are set to begin a 3-game series at Chase Field on Monday night. San Francisco will send Robbie Ray to the mound, while Zac Gallen will toe the rubber for the home team. Ray has seen his fair share of struggles on the road this season, as his ERA jumps from 1.91 at home to 4.50 on the road. The Diamondbacks hit lefties exceptionally well, and they should be able to find some success against the 34-year-old southpaw. Specifically, Arizona ranks 3rd in baseball with a .266 batting average and 6th with a .742 OPS against lefties this season. Ray could have his hands full here.

Gallen is having a rough month of May. The Arizona right-hander has allowed 19 hits and 14 earned runs over 3 starts and 14.1 innings of work to begin the month. After ending April with a 3.14 ERA on the season, Gallen’s ERA now sits at 5.02. He seems to have lost control of the strike zone, as he’s issued 7 walks over his last 3 starts after collecting just 7 total walks over his first 6 starts of the season. Arizona’s bullpen has also been unreliable, ranking 23rd in the league with a 4.50 ERA. All in all, both offenses seem to have the edge in this NL West matchup.

Giants vs Diamondbacks prediction: Over 9 (-115) available at time of publishing. Playable to -120.