Arizona Diamondbacks vs Seattle Mariners Prediction, 5/31/2026 MLB Picks, Best Bets & Odds

Game: Arizona Diamondbacks vs Seattle Mariners

Date: Sunday, May 31, 2026

Location: T-Mobile Park in Seattle, WA

TV: MLB.TV

Odds/Point Spread: Arizona (+125) Seattle (-150)

T-Mobile Park is the location where the Seattle Mariners (28-29) will attempt to beat the Arizona Diamondbacks (31-24) on Sunday. The moneyline on this matchup has the Diamondbacks at +125 and the Mariners are sitting at -150. The total is 8.5. The pitchers taking the mound are Merrill Kelly and Luis Castillo.

As a squad, the Arizona Diamondbacks are recording 4.6 runs per game, which has them at 9th in baseball. They are sitting with 255 runs scored while holding a team on-base percentage of .314. The Diamondbacks have earned 103 two-baggers as a squad and have knocked 48 balls out of the park. They have accumulated 246 RBI's and 453 hits on the season, while their team batting average sits at .248. Arizona is slugging .402 and have struck out 416 times, while taking a walk on 169 occasions.

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Their strikeout to walk ratio is 2.42 and the pitching staff sits with a WHIP of 1.24. Diamondbacks pitchers have given up 58 long balls and 241 total runs (13th in MLB). Arizona has conceded 439 base hits (8.1 per 9 innings) and also 217 earned runs. The Diamondbacks have an ERA of 4.02 on the year (15th in MLB), and the staff has rung up 392 hitters. They have walked 162 batters and their FIP sits at 4.12 as a team so far this season.

The Diamondbacks relief pitchers have recorded a save percentage of 64.0% and have stepped onto the mound in 65 save situations. They have earned 16 saves this year and have blown 9 of their 25 save opportunities. The relief pitchers have inherited 75 runners over the course of the season and 25.3% of them crossing the plate. Diamondbacks relief pitchers have come into the game with opponents on base 51 times in addition to having 69 appearances in high leverage situations. The Diamondbacks have dispatched 180 relievers to the mound this season. The bullpen have recorded 39 holds this season (6th in the league).

The Arizona Diamondbacks have a total of 1,458 putouts for the season, as well as 470 assists and 22 errors. Their fielding percentage is holding steady at .989 which is 7th in baseball, and have a total of 36 double plays. The Diamondbacks have turned 72.0% of balls in play into outs out of their 4,374 innings, ranking them 4th in pro baseball.

Kelly has taken the mound for 1,056 frames and is sitting with 942 punch outs during his career. His earned run average is 3.83 (450 earned runs allowed) and he has a career WHIP of 1.207. He has given up 955 base hits (8.1 hits per 9 innings) and has 320 walks. Kelly (70-56 career mark) sits with a FIP of 3.78 while he has faced 4,350 opposing hitters in the major leagues.

The Seattle Mariners hold an OBP of .317 and a batting average of .230 for the year. They have been called out on strikes on 504 occasions (7th in baseball) and have a total of 435 hits. Seattle has a total of 66 home runs over the course of the season as well as 234 RBIs. The Mariners hold a team slugging percentage of .383 and they average 4.21 runs per game (18th in the league). They have 79 two-baggers, while taking a walk 208 times and notching 240 runs.

The Mariners hold a team WHIP of 1.217 and have a FIP of 3.59 as a squad so far this season. They rank 25th in the league as a staff in total hits conceded with 469. The Seattle pitching staff have yielded 216 runs so far this year while having an ERA of 3.54 (199 earned runs surrendered). Their strikeout to walk ratio sits at 8.60 (485 strikeouts vs 147 free passes). They have allowed 54 dingers and they yield 3.84 runs per 9 innings (5th in the league).

Seattle bullpen pitchers have an inherited score percentage of 16.1% out of their 56 inherited runners. Their bullpen pitchers have stepped onto the hill 67 times in high leverage situations and on 42 occasions with runners on. With 52 save situations, the Mariners have 30 holds in addition to 8 blown saves. They rank 15th in baseball with a save rate of 63.6%, and they have sent 173 relief pitchers onto the diamond so far this year.

In 4,557 innings played, the Mariners have earned a efficiency on defense of 69.1% (24th in professional baseball). The Seattle Mariners have turned 52 double plays and own a fielding percentage of .988 (8th in MLB). The Mariners have racked up 471 assists, 24 errors and have 1,519 putouts during this campaign.

In his pro baseball career, Castillo has surrendered 1,264 base knocks while he has tallied 1,546 strikeouts in 1,460 innings pitched. Castillo (85-89 win-loss mark in his career) is the owner of a 3.64 ERA while allowing 7.8 hits per 9 innings. He has given up a total of 590 earned runs while earning a WHIP of 1.189 and a FIP of 3.6. His strikeout to walk ratio is 3.27 and he has gone up against 6,054 batters thus far in his career.

Who will win tonight's MLB game against the spread or moneyline?

Tony Sink's Pick: Take Arizona (+125)

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