Walk-Off Wagers: MLB Best Bets Today (Predictions for Mets-Pirates, Yankees-Mariners, D-Backs-Giants)

Breaking down the best bets for the MLB action on Tuesday, May 13, including a pick for the Yankees-Mariners matchup.

New York Yankees starting pitcher Max Fried has led his team to an 8-0 record in the 2025 season. / Vincent Carchietta-Imagn Images

Looking to bet on the loaded Major League Baseball slate on Tuesday night? 

You’ve come to the right place, as every day the SI Betting team shares our best bets for the day’s MLB action.

On Tuesday, the New York Yankees and New York Mets are both heavily favored in their respective matchups, and I’m backing both squads to win – albeit in different ways. 

Out West, the NL West race continues to heat up in Game 2 between the Arizona Diamondbacks and San Francisco Giants after Arizona pulled out a 2-1 win in the series opener on Monday. Who has the edge in Tuesday’s contest?

I have picks for all of these games to help bettors navigate a major 15-game slate in MLB. 

MLB Best Bets for Tuesday, May 13

Odds via DraftKings Sportsbook.

• Arizona Diamondbacks-San Francisco Giants First 5 Innings UNDER 4.5 (-145)
• New York Yankees Moneyline (-142) vs. Seattle Mariners
• New York Mets -1.5 (-118) vs. Pittsburgh Pirates

Arizona Diamondbacks-San Francisco Giants First 5 Innings UNDER 4.5 (-145)

The Diamondbacks have one of the best offenses in Major League Baseball this season, ranking fourth in OPS, but I think Tuesday’s matchup between these divisional foes will be a low-scoring one.

Both starters in this game – San Francisco’s Robbie Ray and Arizona’s Brandon Pfaadt – have gotten off to strong starts in 2025, so I’m looking to the UNDER in the first five innings for my best bet.

This season, Ray has a 2.84 ERA, and he only has one start where he’s given up more than three earned runs. In fact, the former Cy Young award winner has led the Giants to a perfect 8-0 record in his starts, and he’s put together an impressive 1.19 WHIP to go along with his ERA. 

On the Arizona side of things, Pfaadt is coming off 6.1 innings of scoreless ball in a win over the Los Angeles Dodgers, lowering his ERA to 3.28 in the process. He also has done a solid job of limiting baserunners, posting a 1.22 WHIP, and he’s allowed three or fewer earned runs in six of his eight starts in 2025.

While Pfaadt and Ray are both going to need to have strong games to keep this total below 4.5 in the first five frames, Ray has put together four straight outings with two or fewer earned runs allowed. 

Since the Arizona bullpen has a 4.95 ERA this season, I prefer this play on the total much more than a full-game UNDER on Tuesday night. 

New York Yankees Moneyline (-142) vs. Seattle Mariners

So far this season, the Yankees have been an amazing bet when lefty Max Fried takes the mound, winning all eight of his starts. 

Fried has been terrific in his first season in pinstripes, posting a 1.05 ERA in eight starts while allowing just 36 hits across 51.2 innings of work. The lefty hasn’t allowed more than two earned runs in a single start this season, and that’s a huge reason why the Yankees are road favorites in this matchup. 

New York won the series opener against the Mariners on Monday night, putting up 11 runs and showcasing why it has the No. 1 offense in basketball. The Yankees are the top team in the league in runs scored, OPS, home runs, batting average and on-base percentage.

The Mariners have also been a solid offense this season, but I’m not sold on them beating Fried with Bryan Woo on the mound. Woo has a 3.25 ERA in seven starts this season, but he’s coming off a rough outing against the A’s where he allowed eight hits and five runs. 

Overall, Woo has been solid this season (he ranks in the 81st percentile in expected ERA), but can he shut down the game’s best offense? 

I lean with Fried and the Yankees in this one given all of their success in his starts. 

New York Mets -1.5 (-118) vs. Pittsburgh Pirates

The Pittsburgh Pirates remain dead last in MLB in runs scored after putting up just three runs to waste yet another gem from ace Paul Skenes on Monday night. 

Now, Pittsburgh is a massive underdog against Kodai Senga and the Mets in Game 2 of this series. Senga has been lights out in 2025, posting a 1.16 ERA across seven appearances. 

While the Mets are shockingly just 4-3 in those games, Senga has not allowed more than two earned runs in a single outing.

That bodes well for New York on Tuesday, as it takes on Mitch Keller (4.50 ERA), who has given up three or more runs in five of his eight outings. As a result, the Pirates are just 2-6 when he takes the mound this season. 

New York also has a much better offense than Pittsburgh, ranking seventh in MLB in runs scored and fifth in OPS. 

Pittsburgh’s lack of run support has led to it posting the second-worst run line record (16-26) in MLB this season. I’ll gladly fade the Pirates on Tuesday night.

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