Walk-Off Wagers: MLB Best Bets Today (Predictions for Astros-Rays, Cubs-Marlins, Red Sox-Mets, Logan Webb)

Breaking down the best bets for the MLB action on Wednesday, May 21, including a pick for the Red Sox-Mets series finale.

The Red Sox are favored at home with Garrett Crochet on the mound. / Eric Canha-Imagn Images

Several MLB series wrap up on Wednesday, May 21 ahead of the weekend, and that means we have a ton of afternoon baseball to dive into.

Eight different games have a first pitch scheduled before 4 p.m. EST, and I’m eyeing three of those matchups in today’s best bets, including a player prop for San Francisco Giants ace Logan Webb.

Then, later in the night, the Boston Red Sox send ace Garrett Crochet to the mound, and he may be a little undervalued against a New York Mets team that is just 3-6 in Tylor Megill’s outings this season.

With baseball going on basically all day, here’s a look at my favorite picks for Wednesday’s action. 

MLB Best Bets for Wednesday, May 21

Odds via DraftKings Sportsbook.

• Houston Astros Moneyline (-142) vs. Tampa Bay Rays
• Chicago Cubs-Miami Marlins OVER 9 (+100)
• Logan Webb UNDER 2.5 Earned Runs Allowed (-160)
• Boston Red Sox Moneyline (-148) vs. New York Mets

Houston Astros Moneyline (-142) vs. Tampa Bay Rays

Houston Astros youngster Hunter Brown is making a real case to be an All-Star this season. He has a 1.43 ERA across nine starts, leading Houston to a 6-3 record in those games.

Brown is coming off eight innings of three-hit, one-run ball in his last outing, and he’s given up just nine earned runs all season long.

That bodes well for Houston on the road on Wednesday afternoon against Taj Bradley and the Tampa Bay Rays. The Rays have struggled at home this season – they’re playing at the New York Yankees’ spring training facility – winning just 12 of 30 games.

While Tampa Bay picked up a win on Tuesday, the Astros have a significant advantage on the mound in this game. Bradley has struggled in May, allowing nine runs in 15.1 innings of work (5.28 ERA).

Tampa Bay is 5-4 in his nine outings, but the righty has an ERA pushing 5.00. The Astros also have a better bullpen ERA than the Rays this season. Neither of these teams has been elite on offense – they both rank in the bottom 10 in the league in OPS – but Brown has been too good to open 2025 to pass up at such a short price on Wednesday. 

Chicago Cubs-Miami Marlins OVER 9 (+100)

The OVER in Miami Marlins games is the best trend in baseball right now, and the Chicago Cubs have done a great job feeding into it.

In the first two games in this series, the Cubs and Marlins have combined for 15 runs in each matchup, soaring past the total in both contests. Now, the total is set at even money to go OVER nine runs on Wednesday afternoon.

This season, Miami is 29-18 to the OVER – the second-best mark in MLB. The only team that is better? The Cubs are 29-16-14. They have hit the OVER in 64.4 percent of their games.

Wednesday’s pitching matchup could be a good one for a high-scoring affair as well. Cade Horton is on the mound for Chicago, and he’s allowed at least three runs in each of his outings this season, giving up 11 hits in just nine innings of work.

On the Miami side, Max Meyer has come back to earth after a fast start to the campaign, allowing four or more runs in each of his three May outings. He has a 7.16 ERA this month, allowing 20 hits in 16.1 innings of work.

After giving up 21 runs in the first two games of this series, I can’t trust this Miami pitching staff to keep the Cubs in check on Wednesday. Chicago ranks No. 1 in MLB in runs scored, fourth in OPS and fifth in batting average.

With two struggling young pitchers on the mound, the OVER is an easy bet in this series finale. 

Logan Webb UNDER 2.5 Earned Runs Allowed (-160)

This season, Webb has been great for the Giants, posting a 2.42 ERA and 2.08 FIP across 10 starts.

He has a solid matchup on Wednesday afternoon, as the Kansas City Royals are just 26th in MLB in OPS and 27th in runs scored in the 2025 season.

Webb has given up two or fewer earned runs in seven of his 10 starts in the 2025 season, and he’s been lights out this month, posting a 1.64 ERA in three starts. Webb has tossed at least seven innings in each of his May outings. 

I’m buying the Giants' ace in this matchup, and his advanced numbers show that he’s been one of the better pitchers in baseball in 2025. Webb ranks in the 84th percentile in expected ERA, 85th percentile in barrel percentage (he’s inducing a lot of weak contact), and 79th percentile in strikeout percentage.

I’ll back him to keep his strong month of May going on Wednesday.  

Boston Red Sox Moneyline (-148) vs. New York Mets

So far in the 2025 season, Crochet only has one outing where he’s given up more than two earned runs, leading Boston to a 6-4 record in his 10 starts.

The lefty enters this matchup with the Mets with a 2.00 ERA and 1.06 WHIP, as he’s allowed just 46 hits in 63.0 innings of work.

New York has dropped three games in a row and four of its last five, and I’m far from sold on the Mets with Megill on the mound. The righty has led New York to just a 3-6 record in his outings this season, and he’s given up at least four runs in all three of his starts in May.

Megill has failed to get through five innings in back-to-back starts, and he’s seen his expected ERA jump to 3.51 this season after what was a strong start to the campaign. 

While New York is nine games over .500 this season, a lot of that work has been done at home, where it is 17-5. On the road, the Mets are just 12-15. 

I’ll back Boston to complete the series sweep with its ace on the bump.

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Odds refresh periodically and are subject to change.

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