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The Seattle Mariners hope to extend a five-game winning streak by picking up a sweep over the Arizona Diamondbacks this afternoon.
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Bryce Miller has been impressive since returning from injury, and my Diamondbacks vs. Mariners predictions explain his slider will neutralize the visitors while Merrill Kelly has a rough day.
Here are my MLB picks for May 31.
Who will win Diamondbacks vs Mariners today: Mariners -1.5 (+155)
After a brutal start to the season, Merrill Kelly’s posted four consecutive quality starts with a .237 wOBA — but I’m not convinced.
I’m not buying it when a career ground-ball pitcher allowed fly balls (49.4%) and hard hits (41.4%) at the rate he did in those starts — especially not while posting a 0.60 GB/FB ratio.
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The Seattle Mariners rank sixth in HR/FB rate (14.6%) over the past two weeks with a 0.88 GB/FB ratio.
Kelly ranks in the bottom percentile in both barrel rate and xERA. I’m backing the Mariners to punish him and cover up to +130.
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COVERS INTEL:
Kelly’s fastball (7.9%) and cutter (11.1%) putaway rates have plummeted from last season, while Seattle’s 45.3% FB% against those pitches is the league’s seventh-highest this month.
Diamondbacks vs Mariners Over/Under pick: Under 7.5 (-114)
While I’m expecting the Mariners to win easily, I am taking the Under to -120.
Bryce Miller has added 2 to 3 mph onto all of his pitches and has tripled his slider usage from a season ago. That breaking ball is generating a 43.3% whiff rate thanks to an additional 2.6 inches of induced vertical break.
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That is a devastating equalizer against the Arizona Diamondbacks, who have a league-leading 48.2% pull rate over the last two weeks.
Seattle’s pen has been outstanding this month, ranking fourth in xFIP (3.56), sixth in K% (24.4%), and sixth in wOBA (.290).
Jason Ence’s 2026 Transparency Record
ML/RL bets: 9-12, -3.94 units
Over/Under bets: 13-8, +4.28 units
Diamondbacks vs Mariners odds
Moneyline: Diamondbacks +133 | Mariners -138
Run line: Diamondbacks +1.5 (-156) | Mariners -1.5 (+150)
Over/Under: Over 7.5 (+100) | Under 7.5 (-104)
Diamondbacks vs Mariners trend
The Seattle Mariners have covered the run line in four of their last five games (+4.80 Units / 96% ROI). Find more MLB betting trends for Diamondbacks vs. Mariners.
How to watch Diamondbacks vs Mariners and game info
Location
T-Mobile Park, Seattle, WA
Date
Sunday, May 31, 2026
First pitch
4:10 p.m. ET
TV
DBacks.TV, Mariners.TV
Diamondbacks starting pitcher
Merrill Kelly
(5-3, 5.25 ERA)
Mariners starting pitcher
Bryce Miller
(1-0, 2.25 ERA)
Diamondbacks vs Mariners latest injuriesDiamondbacks vs Mariners weather
Odds are correct at the time of publishing and are subject to change.
Not intended for use in MA.
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