Diamondbacks vs Giants Prediction, Odds, Moneyline, Spread & Over/Under for May 20

Odds updated as of 11:11 p.m.

Wednesday's slate in the MLB includes a matchup between the Arizona Diamondbacks and the San Francisco Giants.

Here's everything you need to know before checking out today's MLB odds and spreads on FanDuel Sportsbook.

Diamondbacks vs Giants Game Info

• Arizona Diamondbacks (23-23) vs. San Francisco Giants (20-28)
• Date: Wednesday, May 20, 2026
• Time: 3:40 p.m. ET
• Venue: Chase Field -- Phoenix, Arizona
• Coverage: Dbacks.TV and NBCS-BA

Diamondbacks vs Giants Odds & Moneyline

• All MLB odds, betting lines and prop bets are available on FanDuel Sportsbook.
• Moneyline: ARI: (-126) | SF: (+108)
• Spread: ARI: -1.5 (+164) | SF: +1.5 (-200)
• Total: 9 -- Over: (-105) | Under: (-115)

Diamondbacks vs Giants Probable Starting Pitchers

Probable Pitchers: Merrill Kelly (Diamondbacks) - 3-3, 5.91 ERA vs Tyler Mahle (Giants) - 1-5, 5.59 ERA

The Diamondbacks will give the ball to Merrill Kelly (3-3, 5.91 ERA), who is eyeing win No. 4 on the season, and the Giants will counter with Tyler Mahle (1-5, 5.59 ERA). Kelly's team is 3-3-0 against the spread in his starts this season. Kelly's team is 1-1 this season when he starts and they're favored on the moneyline. The Giants have gone 3-6-0 ATS in Mahle's nine starts that had a set spread. The Giants are 2-5 in Mahle's seven starts this season that they were the underdog on the moneyline.

Diamondbacks vs Giants Prediction & Pick

All MLB win probability predictions and picks are according to numberFire.
Prediction: Diamondbacks win (53.3%)

Diamondbacks vs Giants Moneyline

• The Diamondbacks vs Giants moneyline has Arizona as a -126 favorite, while San Francisco is a +108 underdog on the road.

Diamondbacks vs Giants Spread

• The Diamondbacks are favored by 1.5 runs at home versus the Giants. The Diamondbacks are +164 to cover the spread, while the Giants are -200.

Diamondbacks vs Giants Over/Under

• The over/under for the Diamondbacks versus Giants game on May 20 has been set at 9, with -105 odds on the over and -115 odds on the under.

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Diamondbacks vs Giants Betting Trends

• The Diamondbacks have come away with 10 wins in the 16 contests they have been listed as the favorites in this season.
• Arizona has a record of 5-3 when favored by -126 or more this year.
• The Diamondbacks' games have gone over the total in 23 of their 45 opportunities.
• The Diamondbacks are 27-18-0 against the spread in their 45 games that had a posted line this season.
• The Giants have won 13 of the 34 games they were listed as the moneyline underdog this season (38.2%).
• When playing as a moneyline underdog with odds of +108 or longer, San Francisco has gone 10-12 (45.5%).
• The Giants have combined with opponents to hit the over on the total 21 times this season for a 21-24-3 record against the over/under.
• The Giants are 20-28-0 against the spread this season.

Diamondbacks Player Leaders

• Ildemaro Vargas leads Arizona with a slugging percentage of .544, fueled by 17 extra-base hits. He has a .335 batting average and an on-base percentage of .356.
• He ranks second in batting average, 50th in on-base percentage, and 13th in slugging among all qualifying hitters in MLB.
• Vargas hopes to build on a two-game hitting streak in this matchup. In his last five games he is hitting .333 with a double and five RBIs.
• Corbin Carroll leads Arizona with 44 hits and an OBP of .392 this season. He's batting .284 and slugging .555.
• He is 32nd in batting average, 14th in on-base percentage and 11th in slugging in the majors.
• Carroll heads into this matchup looking to extend his seven-game hit streak. In his last 10 outings he is hitting .353 with four doubles, a triple, two home runs, nine walks and four RBIs.
• Nolan Arenado is batting .272 with a .463 slugging percentage and 25 RBI this year.
• Arenado enters this matchup with two games in a row with at least one hit. During his last five outings he is hitting .313 with three doubles, a home run, five walks and seven RBIs.
• Geraldo Perdomo has been key for Arizona with 34 hits, an OBP of .344 plus a slugging percentage of .353.
• Perdomo takes a four-game hitting streak into this matchup. During his last five outings he is hitting .250 with a double and five walks.

Giants Player Leaders

• Luis Arraez has accumulated a team-high OBP (.365) and slugging percentage (.432). He's batting .324.
• Including all the qualified hitters in MLB, his batting average ranks fifth, his on-base percentage is 39th, and he is 63rd in slugging.
• Casey Schmitt's 44 hits lead his team. He has a batting average of .295 while slugging .523 with an on-base percentage of .342.
• Including all qualifying hitters, he ranks 21st in batting average, 67th in on-base percentage and 19th in slugging percentage.
• Jung Hoo Lee has 10 doubles, a triple, three home runs and 10 walks while batting .268.
• Rafael Devers is batting .240 with 10 doubles, five home runs and 13 walks.

Diamondbacks vs Giants Head to Head

• 5/18/2026: 12-2 ARI (Favorite: Diamondbacks, Spread: -1.5, Total: 9, Favorite Moneyline: -136, Underdog Moneyline: +116)
• 9/17/2025: 5-1 SF (Favorite: Diamondbacks, Spread: -1.5, Total: 9, Favorite Moneyline: -108, Underdog Moneyline: -108)
• 9/16/2025: 6-5 ARI (Favorite: Diamondbacks, Spread: -1.5, Total: 9, Favorite Moneyline: -130, Underdog Moneyline: +110)
• 9/15/2025: 8-1 ARI (Favorite: Diamondbacks, Spread: -1.5, Total: 9, Favorite Moneyline: -132, Underdog Moneyline: +112)
• 9/10/2025: 5-3 ARI (Favorite: Giants, Spread: -1.5, Total: 8.5, Favorite Moneyline: -126, Underdog Moneyline: +108)
• 9/9/2025: 5-3 SF (Favorite: Giants, Spread: -1.5, Total: 7.5, Favorite Moneyline: -142, Underdog Moneyline: +120)
• 9/8/2025: 11-5 SF (Favorite: Giants, Spread: -1.5, Total: 7.5, Favorite Moneyline: -174, Underdog Moneyline: +146)
• 7/3/2025: 7-2 SF (Favorite: Giants, Spread: -1.5, Total: 8.5, Favorite Moneyline: -126, Underdog Moneyline: +108)
• 7/2/2025: 6-5 SF (Favorite: Diamondbacks, Spread: -1.5, Total: 8.5, Favorite Moneyline: -146, Underdog Moneyline: +124)
• 7/1/2025: 8-2 ARI (Favorite: Diamondbacks, Spread: -1.5, Total: 9, Favorite Moneyline: -130, Underdog Moneyline: +110)

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