⚾ Padres vs. Mariners Win Probability: Who Will Win Tonight’s MLB Game? (May 17)

An inconsistent Mariners team has now dropped three of its last four games, including the first two during a series against the San Diego Padres.

The Padres vs. Mariners win probability from the prediction market apps heavily favors the Mariners to avoid a sweep in the prime-time cap to a Sunday of baseball starting tonight at 7:20 p.m. ET from T-Mobile Park (Peacock).

They're hovering around a 60% favorite, largely due to the brilliance of tonight's starter George Kirby, and especially as San Diego counters with journeyman Lucas Giolito.

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🏆 Who will win Padres vs. Mariners? Live MLB win probability

Once again the Mariners are a heavy home favorite while getting a 59% win probability amid just over $63,500 in trading volume. The same was true yesterday ahead of first pitch, and that projection landed with a thud when Seattle failed to beat up on Walker Buehler en route to losing 7-4.

Tonight should be a different story though with the Padres needing to trot out Giolito to make his season debut for them as an injury replacement for the ailing Matt Waldron. Giolito was often subpar during his minor-league rehab starts while posting a 4.76 ERA.

He filled a role nicely for the Boston Red Sox last year while putting up a 3.41 ERA. But his underlying metrics left much to be desired, and especially Giolito's far higher expected ERA of 5.06, according to Baseball Savant.

His presence alone is why the Mariners are deserved strong favorites, and we may see their probability creep up even a little higher ahead of first pitch. That's especially true with Kirby opposing Giolito. Kirby's strikeouts may be down from a 9.8 K/9 last year to 7.3 now, but he's inducing weak contact at a high level, with a barrel rate in the 89th percentile and a sky-high groundball rate of 57.0%, up from 43.9% last year.

My prediction: Mariners win. Kirby has also dazzled while posting an opposing slugging percentage of .237, down from .392 last year.

💣 Who will hit a home run in Padres vs. Mariners?

Mariners center fielder Julio Rodriguez is the easy front-runner in this market while getting a 17% probability to go deep, giving him a sizable edge over the Padres' Jackson Merrill at 13% and Manny Machado at 12%.

Rodriquez could very well grow his lead a little further, as he's been heating up lately. A tough March and April when he posted a .678 OPS is behind him, and now midway through May that mark sits at .890 for the month. Rodriguez has arrived there while clubbing five homers across 14 games in May.

He gets an appealing matchup against Giolito. The right-hander sat out 2024 due to an injury, and his strikeouts in 2025 declined dramatically compared to 2023 (10.0 K/9 to 7.5). Combine that with underwhelming fastball velocity (93.3 mph average), and there will be plenty of chances to tee off.

My prediction: Julio Rodriguez to hit a home run. Opposing hitters posted a .523 expected slugging last year against Giolito's four-seamer. For more home run analysis, see the rest of our home run predictions from our MLB expert Mike Spector.

⚾ Will there be a run in the first inning of Padres vs. Mariners?

This market began at 43% before sharply dipping and overcorrecting to 35%. The chances of a first-inning run have since settled in around 45%, which still feels a smidge high considering Kirby's dominance and the Padres' tendencies.

San Diego is the league's best NRFI team at 33-12, and it's especially efficient in that regard away from homer-friendly Petco Park, with the Padres' NRFI record sitting at 17-5 on the road.

The Mariners are among the worst NRFI teams at 20-27. However, slugger Cal Raleigh is in the early days of being out a few weeks due to an injury, which is a significant blow to an already middling offense that ranks 18th in scoring leaguewide.

Combine that with Kirby minimizing quality contact through his barrel rate allowed that's in the 89th percentile, and there's the recipe for a blank first frame.

My prediction: No run in the first inning. Opposing batters are also putting up a .190 expected batting average against Kirby's lethal sweeper.

📊 Padres vs. Mariners win expectancy

Win expectancy based on Kalshi percentages at time of publish.

📺 How to watch Padres vs. Mariners

• Date: Sunday, May 17
• First pitch: 7:20 p.m. ET
• Ballpark: T-Mobile Park (Seattle)
• TV: Peacock
• Streaming: MLB.TV
• Padres starter: Lucas Giolito (10-4, 3.31 ERA in 2025)
• Mariners starter: George Kirby (5-2, 2.84 ERA)