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MLB Picks, Best Bets, Props, Predictions Today – September 21

MLB Picks, Best Bets, Props, Predictions Today – September 21 article feature image
6 min read
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Photos by Imagn Images.

We have a 15-game slate on Sunday, and several of these matchups have massive playoff implications.

So there's a lot of baseball on the schedule today, but we have you covered. Our MLB betting experts and systems have sifted through the latest MLB odds and have made their predictions below.

So, continue reading for today's MLB best bets.

Quickslip

MLB Best Bets Today

The team logos in the table below represent each of the matchups that our MLB betting staff is targeting from today's slate of games. Click on the team logos for any of the matchups below to navigate to a specific bet discussed in this article.

GameTime (ET)Pick
New York Yankees LogoBaltimore Orioles Logo
1:35 p.m.
Washington Nationals LogoNew York Mets Logo
1:40 p.m.
Philadelphia Phillies LogoArizona Diamondbacks Logo
4:10 p.m.
Boston Red Sox LogoTampa Bay Rays Logo
8:10 p.m.
Specific betting recommendations come from the sportsbook offering preferred odds as of writing. Always shop for the best price using our MLB Odds page, which automatically surfaces the best lines for every game.

Bet Labs' Yankees vs Orioles Best Bet: Trust The Arms

New York Yankees Logo
Sunday, September 21
1:35 p.m. ET
MLB.TV
Baltimore Orioles Logo
Under 8.5 (-110)
bet365 Logo

By Bet Labs

This matchup between the New York Yankees and Baltimore Orioles sets up well for a system play on the under: "Daytime Unders with Efficient Arms".

The angle zeroes in on day games (11:00 a.m.–2:59 p.m. ET), where scoring often trends lower. Sun and shadows affect hitter visibility, while the quicker turnaround from the previous night limits offensive rhythm.

The system specifically filters for visiting pitchers with an ERA between 3.00 and 4.76 and a WHIP between 1.07 and 1.39. That profile captures efficient arms—capable of suppressing damage—without being priced like top-tier aces.

When these conditions align, the game tends to play slower, and public perception often overshoots reality on the total. Yankees vs. Orioles checks the boxes today—making the under a sharp angle to consider.

MLB Icon
Evan Abrams / Bet Labs – Daytime Unders with Efficient Arms
the game started between 11:00 and 14:59 ET
the home team's number of hits per game is between 7.81 and 8.24
the visiting team's starting pitcher's ERA is between 3 and 4.76
the visiting team's starting pitcher's WHIP is between 1.07 and 1.39
the game is played during the Regular season
betting on the Under
$1655
WON
281-247-34
RECORD
53%
WIN%

Pick: Under 8.5 (-110)



Grant Neiffer's Nationals vs Mets Best Bet: Believe in Brett Baty Power

Washington Nationals Logo
Sunday, September 21
1:40 p.m. ET
MLB.TV
New York Mets Logo
Brett Baty Over 0.5 Home Runs (+700)
bet365 Logo

By Grant Neiffer

Going hard on the Mets as the spot is far too good today. Irvin has been a complete gas can for power this season, allowing a massive 2.22 HR/9 to lefties and an above-average 1.43 HR/9 to righties.

The ballpark and weather aren't great, but that is more than baked into the price. I have the true odds on Baty under +600 today, making this a great EV bet.

Pick: Brett Baty Over 0.5 Home Runs (+700)



Bet Lab's Phillies vs Diamondbacks Best Bet: Expect a Lot of Runs

Philadelphia Phillies Logo
Sunday, September 21
4:10 p.m. ET
MLB.TV
Arizona Diamondbacks Logo
Over 9 (-110)
bet365 Logo

By Bet Labs

Tonight’s matchup between the Philadelphia Phillies and Arizona Diamondbacks fits a late-season totals system that has consistently identified value on the over.

The angle, highlighted by Evan Abrams, zeroes in on late-season games (August–October) played in high-variance hitting environments like Colorado, Arizona, and Washington. When the closing total is 10.5 or lower, these parks have historically produced more offense than the market anticipates.

In Arizona, dry desert air and hitter-friendly park conditions combine with expanded rosters and bullpen fatigue to create volatile scoring environments. Meanwhile, the betting market often leans toward unders at this time of year, influenced by narratives around playoff pressure and tired bats. That disconnect allows overs to cash at a profitable rate.

With the Phillies bringing one of the league’s deepest lineups into Chase Field and the Diamondbacks capable of contributing runs at home, the ingredients align for another potential over.

MLB Icon
Evan Abrams – Late Season Overs, Lower Totals — COL, ARI, WAS Home (YEAR)
the game was played during the 2025 or 2024 or 2023 or 2022 or 2021 or 2018 or 2017 or 2016 or 2015 or 2014 season
the game was played in September or August or October
the closing total is between 0 and 10.5
betting on the Over
the game is played during the Regular season
the home team is Washington Nationals or Arizona Diamondbacks or Colorado Rockies
$5739
WON
352-271-31
RECORD
57%
WIN%

Pick: Over 9 (-110)



Doug Ziefel's Red Sox vs Rays Best Bet: Team Total Pick

Boston Red Sox Logo
Sunday, September 21
8:10 p.m. ET
NESN
Tampa Bay Rays Logo
Rays Team Total Over 3.5 (-115)
bet365 Logo

By Doug Ziefel

It's safe to say the Red Sox rookie left-hander has been extremely impressive to this point. Through his first two career starts, he's allowed just one run on 10 hits and has struck out 18.

Impressively, he's allowed zero barrels and has an average exit velocity of just 86.1. However, while there are no clear signs of regression, this will be just his third career start, and it's going to take place in a hitters' ballpark against a lineup that has hit lefties very well lately.

Over the last month, the Rays rank 13th in wRC+ and OPS against lefties. This Tampa Bay team has also hit very well at George M. Steinbrenner Field, boasting a .311 BABIP and a 107 wRC+.

Also, Early is just a piece of the Red Sox pitching puzzle tonight as he is expected to go around five innings. Behind him is a question mark, as all four of Boston's high-leverage relievers threw yesterday.

With regression coming for Early and the Red Sox bullpen taxed, the door is wide open for another strong offensive performance from the Rays at their home park.

Back them by taking their team total over.

Pick: Rays Team Total Over 3.5 (-115)



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