MLB Best Bets Today: Player Props for Monday, September 21

MLB Betting Expert Juan Pablo Aravena digs in Monday, offering up a trio of prop picks and predictions despite an extremely abbreviated slate.
MLB Best Bets Today: Player Props for Monday, September 21
RotoWire
Win your week.
Every lineup, every streamer, every waiver. We make the call.
Every lineup, every streamer, every waiver. We make the call.

Monday's abbreviated MLB slate doesn't provide a huge menu of games, but the player-prop market still offers some appealing opportunities. 

We're targeting plus-money on two established hitters before turning to a strikeout prop in San Francisco, where Zebby Matthews draws an attractive matchup at Oracle Park.

Use the best sportsbook promos from the best MLB betting sites this baseball season. The BetMGM bonus code gets new players one of the best welcome bonuses in the industry.

MLB Best Bets for Monday

Baltimore Orioles vs. Toronto Blue Jays

Alonso has provided plenty of extra-base upside in his first season with Baltimore, averaging 1.88 total bases per game through 155 appearances. The matchup with Trey Yesavage isn't necessarily an easy one, and Alonso is hitless in five at-bats with two strikeouts in their limited previous meetings, but the price compensates for some of that risk. 

Alonso needs only one extra-base hit or a multi-hit performance to cash, and his power makes either route realistic at Camden Yards. Getting +137 on a hitter averaging nearly two total bases per game provides enough upside to attack this number.

Cash in at Caesars Sportsbook this MLB season and use the Caesars Sportsbook promo code for one of the top MLB betting promos.

Washington Nationals vs. Detroit Tigers

  • CJ Abrams Over 1.5 total bases (+110 FanDuel)

Abrams enters Monday with some encouraging contact behind him, recording a hit in four of his last five games while collecting extra bases in three of those contests, including a home run Sunday against St. Louis. 

He'll now face River Ryan, who is scheduled to make his first major-league appearance of 2026 for Detroit. Abrams' combination of contact, extra-base ability and a premium lineup position gives him multiple paths to clearing this number. With Detroit turning to a pitcher without any MLB innings this season, the plus-money price makes Abrams' over an appealing way to target one of Washington's middle-of-the-order hitters.

Minnesota Twins vs. San Francisco Giants

Matthews has been inconsistent, but the ceiling is certainly high enough to attack a modest 4.5-strikeout line. The right-hander owns 107 strikeouts this season and is averaging 4.86 per start, while he's cleared Monday's number in three of his last five outings. More importantly, his latest start produced eight strikeouts against the Yankees, demonstrating the swing-and-miss upside remains intact. 

Matthews is confirmed to start Monday at Oracle Park, carrying a 9-10 record and 4.74 ERA into the matchup. At essentially even-money, five strikeouts is a reasonable target against a San Francisco team that has been one of the biggest disappointments of the 2026 MLB season.

Check in on one of the top sports betting apps when you sign up with the bet365 bonus code for your baseball betting.

MLB Picks Recap

All Plays - 1 Unit

ABOUT THE AUTHOR
37-year-old sports analyst, betting writer and journalist. Fan of every single sport on this earth, but mainly NBA, MLB, NFL, NHL and soccer. Eternal optimistic who, for unknown reasons, chose to root for the Chicago Cubs and Jacksonville Jaguars. Born and raised in Chile.
RotoWire Logo

Continue the Conversation

Join the RotoWire Discord group to hear from our experts and other MLB fans.

Top News

Tools

MLB Draft Kit Logo

MLB Draft Kit

Fantasy Tools

Don’t miss a beat. Check out our 2026 MLB Fantasy Baseball rankings.

Related Stories