Giants vs. Diamondbacks Prediction and Odds: San Francisco Primed to Pull Off Upset on Tuesday

The San Francisco Giants are eight games under .500 and have a minus-47 run differential this season after getting blown out by the Arizona Diamondbacks in Monday’s series opener.

Despite that, San Fran may be worth a look as an underdog in the second game of this series, as it has one of its better pitchers on the mound.

Landen Roupp (3.49 ERA) is looking to win his six game of the 2026 season, and he’ll go up against Arizona righty Ryne Nelson (5.40 ERA), who has not found his groove through nine outings.

Nelson ranks in the second percentile in ground-ball percentage this season, making him a pitcher to fade in the prop market – something I’m doing on Tuesday night.

In addition to a player prop, I’m eyeing a potential upset in this NL West battle, even though the Giants have been pretty bad on the road (10-16) in the 2026 campaign.

Here’s a breakdown of the odds, Tuesday’s best bets and more for Giants vs. Diamondbacks.

Giants vs. Diamondbacks Odds, Run Line and Total

Odds via DraftKings Sportsbook

Spread

Giants -1.5 (+157)
D-Backs +1.5 (-192)

Moneyline

Giants: +104
D-Backs: -125

Total

8.5 (Over -120/Under -101)

Giants vs. Diamondbacks Probable Pitchers

San Francisco: Landen Roupp (5-4, 3.49 ERA)
Arizona: Ryne Nelson (1-3, 5.40 ERA)

Giants vs. Diamondbacks How to Watch

Date: Tuesday, May 19
Time: 9:40 p.m. EST
Venue: Chase Field
How to Watch (TV): NBC Sports Bay Area, DBACKS.TV
Giants record: 20-28
D-Backs record: 23-23

Giants vs. Diamondbacks Best MLB Prop Bets

Giants Best MLB Prop Bet

Rafael Devers to Hit a Home Run (+449)

Can Rafael Devers stay hot? The Giants star has started to turn things around after a slow start, and he’s one of my favorite home run prop targets on Tuesday:

San Francisco Giants star Rafael Devers is starting to heat up, yet he’s still priced at +449 to leave the yard on Tuesday night.

Devers is hitting .333 with three home runs and a .993 OPS over the last two weeks (13 games), and now he takes on the Arizona Diamondbacks and struggling right-hander Ryne Nelson.

This season, Nelson has a 5.40 ERA, allowing nine home runs in nine appearances. Arizona’s bullpen has been pretty shaky behind him as well, allowing 17 home runs in 2026 while posting a 4.41 ERA.

It’s hard to find a better matchup for Devers, especially since four of his five homers have come against righties this season. After an awfully slow start, Devers is starting to live up to his billing in 2026.

I don’t mind him at this price in this NL West battle.

Giants vs. Diamondbacks Prediction and Pick

This season, Roupp has led the Giants to five wins in his nine outings, and his advanced numbers are pretty great:

Expected ERA: 2.73 (88th percentile)
Expected BAA: .208 (87th percentile)
Avg Exit Velocity Against: 86.4 (87th percentile)
Barrel Percentage: 1.7% (96th percentile)
Hard-Hit Percentage: 26.7% (95th percentile)
Strikeout Percentage: 28.9% (87th percentile)

The same can’t be said for Nelson, who ranks in the 13th percentile in barrel percentage and the 15th percentile in hard-hit percentage, posting an expected ERA of 4.49.

The D-Backs are just 2-7 when Nelson is on the mound this season, so there is zero incentive to back them as favorites in this matchup.

The Giants have gotten off to a pretty rough start in 2026, but there’s value in them as a road underdog on Tuesday with Roupp on the mound. I also don’t mind playing San Fran to win the first five innings before the bullpens get involved, but the Giants (3.43 bullpen ERA) have a better pen than the D-Backs (4.41 ERA) so far in 2026.

Pick: Giants Moneyline (+104 at DraftKings)

Odds refresh periodically and are subject to change.

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