MLB Best Bets Today: MLB Betting Picks for Tuesday, July 21
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Cincinnati Reds at Seattle Mariners Best Bets and Predictions
Tuesday night's Reds vs. Mariners matchup features one of the strongest starting pitching advantages on the board, making Cincinnati an attractive value play. Seattle opened as a slight -116 favorite, while the Reds can be found around +107, with the total set at 7.5 runs. First pitch is scheduled for 9:40 p.m. ET at T-Mobile Park.
The biggest reason to back Cincinnati is Chase Burns. The rookie right-hander has been one of baseball's breakout stars, compiling an 11-1 record, 2.54 ERA, 1.11 WHIP and 118 strikeouts over 102.2 innings. Burns has consistently overpowered opposing lineups with elite swing-and-miss stuff, and advanced metrics support his dominance. He's quickly established himself as the Reds' unquestioned ace.
Seattle counters with veteran Luis Castillo, who has endured a difficult 2026 campaign. Castillo enters with a 3-8 record, 4.93 ERA, 1.37 WHIP and 81 strikeouts in 87.2 innings. While he remains capable of flashing top-end stuff, his inconsistency and increased hard contact have made him vulnerable against quality offenses. That's a sizable edge for Cincinnati in the most important matchup of the night.
The Mariners enter 51-50 overall and 30-21 at home, but they've cooled recently, going 4-6 over their last 10 games while being outscored by six runs. Cincinnati owns a 45-54 record and is 23-26 on the road, yet the Reds have also gone 4-6 over their last 10 contests and have enough offensive firepower with Elly De La Cruz and Sal Stewart to capitalize on mistakes. Monday's 8-0 Seattle victory could also create a buying opportunity, as the market may be overreacting to one lopsided result rather than the significant pitching advantage Cincinnati enjoys in Game 2.
Another factor working in Cincinnati's favor is the bullpen. While neither relief corps enters completely fresh, Seattle could once again need multiple high-leverage innings if Castillo exits early, increasing the importance of Burns working deep into the game.
The prediction comes down to trusting the far superior starting pitcher. With Burns carrying an 11-1 record and 2.54 ERA against Castillo's 4.93 ERA, Cincinnati offers value at nearly even money.
Final Prediction: Reds 4, Mariners 2
Best Bet: Reds ML for 1 unit (Circa Sports +107)
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Miami Marlins at Houston Astros Best Bets and Prediction
The Marlins vs. Astros matchup offers one of Tuesday's more intriguing betting opportunities, with Miami available as a slight underdog despite holding advantages in several key statistical categories. The Marlins enter 52-49 overall while Houston is 48-54, and Miami appears to have the edge on the mound with Tyler Phillips facing Tatsuya Imai.
Tyler Phillips has quietly been one of Miami's steadiest starters, posting a 3.48 ERA and 1.39 WHIP across 75 innings while limiting opponents and consistently keeping the Marlins in games. Houston counters with Tatsuya Imai, who owns a 6.06 ERA and 1.50 WHIP over 52 innings. The Astros' right-hander has flashed strikeout upside, but frequent traffic on the bases and inconsistent command have made him difficult to trust.
Miami also enters with the stronger overall statistical profile. The Marlins own a 4.05 team ERA compared to Houston's 4.75 mark while allowing fewer hits and home runs. Offensively, Miami holds advantages in batting average (.252 vs. .241), on-base percentage (.328 vs. .315) and OPS (.736 vs. .726), giving the Marlins more consistent lineup production despite Houston's superior home-run total.
Neither club has been playing its best baseball, with both teams sitting at 3-7 over their last 10 games. However, Miami has consistently been the better team throughout the season, entering Tuesday four games above .500 while Houston remains four games below .500. The Marlins also rank among baseball's best baserunning teams with 104 stolen bases, giving them another way to manufacture runs against an Astros club that has struggled to prevent scoring.
Miami's overall pitching staff has been more consistent throughout the season, and if Phillips can work into the sixth inning, the Marlins should be in position to take advantage of the favorable starting pitching matchup. At plus money, the value lies with the better overall team and the superior starting pitcher.
Final Prediction: Marlins 5, Astros 3
Best Bet: Marlins ML for 1 unit (FanDuel +108)
Detroit Tigers at Chicago Cubs Best Bets and Predictions
The Tigers vs. Cubs matchup presents one of Tuesday's better underdog opportunities, with Detroit listed around even money despite holding a significant edge on the mound. While the Cubs own the superior overall record, the starting pitching mismatch favors the Tigers, making Detroit on the moneyline the preferred betting angle.
Framber Valdez gives Detroit a clear advantage entering Tuesday. The veteran left-hander is 5-6 with a 4.10 ERA and 1.32 WHIP over 107.2 innings, and his underlying metrics remain considerably stronger than his record suggests. Valdez also ranks among the day's better projected starters and consistently generates weak contact. Chicago counters with David Peterson, who has struggled throughout the season, posting a 6.45 ERA and 1.64 WHIP across 82.1 innings. Peterson has allowed frequent baserunners and has been vulnerable to big innings, creating an opportunity for Detroit's lineup to capitalize.
Although the Cubs are 56-44 overall and 29-21 at Wrigley Field, Detroit enters playing its best baseball of the season. The Tigers are 7-3 over their last 10 games with an outstanding 2.10 team ERA, outscoring opponents by 22 runs during that stretch. Chicago has also played well at 6-4, but Detroit's recent pitching has been among the hottest in baseball.
Season-long numbers also support the Tigers' chances. Detroit owns a 3.59 team ERA compared to Chicago's 4.29 mark while allowing significantly fewer home runs (98 versus 154) and posting a better WHIP (1.21 versus 1.27). The Cubs hold offensive advantages in batting average, on-base percentage and OPS, but those edges are partially neutralized by Valdez's ability to keep the ball on the ground and limit hard contact.
With the superior starting pitcher, the stronger overall pitching staff and positive momentum entering the series opener after an 8-6 victory Monday, Detroit offers excellent value at a near pick'em price. When the pitching edge is this pronounced, backing the underdog is the preferred play.
Final Prediction: Tigers 5, Cubs 3
Best Bet: Tigers ML for 1 unit (Circa Sports +105)
Tuesday's Best Bets and Predictions
- Reds ML for 1 unit (Circa Sports +107)
- Marlins ML for 1 unit (FanDuel +108)
- Tigers ML for 1 unit (Circa Sports +105)
