Arizona Diamondbacks vs San Francisco Giants Prediction 5/18/26 MLB Picks Today

The San Francisco Giants and the Arizona Diamondbacks meet Monday in MLB action from Chase Field. We will look at this from a betting perspective and determine the best bets for this game. Here’s a San Francisco Giants vs. Arizona Diamondbacks prediction.

Starting Pitching Matchup

The San Francisco Giants will send out Robbie Ray for the start here and Ray is 3-5 with a 3.04 ERA and 49 strikeouts this season. In his career, Ray is 3-0 with a 3.15 ERA and 21 strikeouts against Arizona. Zac Gallen will start here for Arizona and is 1-4 with a 5.02 ERA and 29 strikeouts this season. In his last five starts against San Francisco, Gallen is 4-1 with a 2.27 ERA and 38 strikeouts.

San Francisco Giants Recap

The San Francisco Giants come into this game looking to add on to their 10-1 win over the Athletics last time out to improve to 20-27 this season. After this series, the Giants will square off against the Chicago White Sox at home.

Giants Win Back-To-Back Games

Luis Arraez has 57 hits with 9 doubles, 2 triples and 16 RBIs while Willy Adames has 44 hits with 14 doubles, 3 home runs and 13 RBIs along with 56 strikeouts. Matt Chapman has 39 hits with 11 doubles, a triple, a home run and 16 RBIs and Jung Hoo Lee has 47 hits with 10 doubles and 17 RBIs. Heliot Ramos has 44 hits with 12 doubles, 4 home runs and 20 RBIs this season. Rafael Devers also has 44 hits with 10 doubles, 5 home runs and 19 RBIs but also has 59 strikeouts this season.

Arizona Diamondbacks Recap

The Arizona Diamondbacks come into this game looking to add on to their 8-6 win over Colorado last time out to sit at 22-23 this season. After this series, the Diamondbacks will take on the Rockies in a series rematch at home.

Diamondbacks Alternate Wins & Losses In 4 Straight

Corbin Carroll has 42 hits including 11 doubles, 4 triples, 7 home runs and 24 RBIs while Alek Thomas has logged 9 doubles with 2 home runs and 10 RBIs as well this season. Ketel Marte has 36 hits with 6 doubles, 5 home runs and 15 RBIs and Geraldo Perdomo has 33 hits, with 7 doubles, 3 triples, 2 home runs and 12 RBIs as well this season. Nolan Arenado also has 39 hits with 7 doubles, 6 home runs and 21 RBIs and Jose Fernandez has 33 hits with 3 home runs and 14 RBIs this season. Ildemaro Vargas also has 51 hits with 8 doubles, 2 triples, 7 home runs and 31 RBIs.

San Francisco Giants @ Arizona Diamondbacks Betting Trends: May 18, 2026

• Probable Starting Pitcher: Zac Gallen      Record this season: 1-4      ERA: 5.02
• Home Record: 1-1
• Last 5 against Giants: 4-1

Why the Arizona Diamondbacks will win

• The Diamondbacks have won eight of their last nine night games against the Giants at Chase Field following a win.
• The Giants have lost each of their last four road games against teams that held a losing record.
• The Diamondbacks have covered the run line in seven of their last eight home games following a road win.
• The Giants have failed to cover the run line in eight of their last 10 games at Chase Field against teams that held a losing record.
• The Diamondbacks have won the first inning in five of their last six night games against NL West opponents that held a losing record.
• The Diamondbacks have led after 3 innings in seven of their last eight games as favorites against National League opponents.
• The Diamondbacks have led after 5 innings in nine of their last 10 night games against NL West opponents that held a losing record.

• Probable Starting Pitcher: Robbie Ray      Record this season: 3-5      ERA: 3.04
• Road Record: 0-4
• Last 5 against Diamondbacks: 3-0

Why the San Francisco Giants will win

• The Giants have won each of their last six night games against NL West opponents that held a losing record.
• The Diamondbacks have lost four of their last six games as favorites after playing the previous day.
• The Giants have covered the run line each of their last six night games against NL West opponents that held a losing record.
• The Diamondbacks have failed to cover the run line in four of their last five games as favorites against NL West opponents following a win.
• The Giants have won the first inning in three of their last four night games at Chase Field.
• The Giants have led after 3 innings in each of their last six night games against NL West opponents that held a losing record.
• The Giants have led after 5 innings in each of their last four night games against NL West opponents that held a losing record.

Total Runs Facts

• Seven of the Giants’ last eight games as underdogs against NL West opponents have gone UNDER the total runs line.
• Seven of the Diamondbacks’ last eight games against National League opponents have gone UNDER the total runs line.
• The ‘Inning 1 UNDER 0.5 runs’ market has hit in each of Robbie Ray’s last six appearances as a starter.
• The ‘Inning 1 OVER 0.5 runs’ market has hit in each of the last four night games between the Giants and Diamondbacks at Chase Field.

Arizona Diamondbacks Player Prop Facts

• Zac Gallen has recorded a win in each of his last five home appearances against the Giants.
• Zac Gallen has recorded five or more strikeouts in each of his 14 previous home appearances against NL West opponents that held a losing record.
• Corbin Carroll has recorded at least one hit in each of his last 17 appearances in night games against NL West teams that held a losing record.
• James McCann has hit a home run in three of his last five appearances with his team as a favorite against the Giants.
• Ildemaro Vargas ranks 3rd amongst qualified players for Batting Average (.333) this season.

San Francisco Giants Player Prop Facts

• Willy Adames has hit a home run in three of the Giants’ last four night games against NL West opponents that held a losing record.
• Matt Chapman has recorded at least one hit in each of his last eight appearances in night games against NL West teams that held a losing record.
• Luis Arraez ranks T2nd in the league in Hits (57) this season.

Matchup/League Facts

• The Diamondbacks rank 1st in the league for triples this season (12).
• The Diamondbacks rank 29th in the league for strikeouts this season (333).
• The Giants rank 30th in the league for runs scored this season (165).
• The Giants rank 30th in the league for RBIs this season (159).

San Francisco Giants vs. Arizona Diamondbacks Prediction

I’m on the Giants in this one. I think that the Giants have an edge here in starting pitching with Robbie Ray going as Ray was solid prior to the start against the Dodgers, which I’m not going to fault anyone for having a rough outing against that Dodger lineup. Zac Gallen’s been getting roughed up in recent starts and I think the Giants draw first blood here. Give me San Francisco.