MLB Expert Picks & Baseball Predictions August 21

Robert Criscola - Betting Analyst at Covers.com
Robert Criscola • Betting Analyst 11+ years betting experience
Updated: Aug 21, 2026 , 11:32 AM ET • 4 min read

Our MLB experts are ready for the weekend with their top plays for Friday's slate! See why the Diamondbacks will win big over the Reds, and much more.

Arizona Diamondbacks MLB Nolan Arenado
Photo By - Reuters Connect. Arizona Diamondbacks third baseman Nolan Arenado (28) high-fives teammates in the dugout after hitting a solo home run.

The weekend has arrived, and so have our MLB expert picks!

See why the Diamondbacks will roll over the Reds, and much more, on Friday, Aug. 21.

MLB expert picks for today

Pick Odds
Jon Metler Jon Metler: CHC ML -104
Dustin Saracini Dustin Saracini: TB ML +113
Joe Osborne Joe Osborne: ARZ -1.5 +150

Prices courtesy of Polymarket.

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Jon Metler's expert pick: Cubs moneyline

Price: 51¢ (-104) at Polymarket

Matthew Boyd has struggled of late, allowing four home runs and seven earned runs in his last outing. But that poor performance may be exactly why we're getting an opportunity in the market, and I think the matchup at T-Mobile Park sets up well for a bounce-back start.

Boyd is a fly-ball pitcher, which can make him vulnerable depending on the ballpark and weather conditions. T-Mobile Park is an ideal setting for him, as the marine layer can limit the carry on fly balls and help mitigate his biggest weakness.

His overall numbers haven't been great this season, but many of his struggles have come at Wrigley Field. On the road, Boyd has posted a 2.57 ERA while allowing just two home runs, compared to 11 at Wrigley.

The Cubs are trading at 51 cents on Polymarket, but I make them closer to a 54-cent favorite, giving us an edge at the current price.

  • Time: 10:10 p.m. ET
  • How to watch: MARQ, Mariners.TV

Dustin Saracini's expert pick: Rays moneyline

Price: 47¢ (+113) at Polymarket

The Rays have lost five of their last seven games, but are in a prime bounce-back spot as underdogs against Trevor Rogers and the Baltimore Orioles on the road.

Yandy Diaz (7-for-13, .591 xSLG), Junior Caminero (3-for-10, .278 xBA), and Ryan Vilade (4-for-4, HR) have all had their way against Rogers, who's coughed up a homer in each of his last three starts.

Going for the Rays is Freddy Peralta, who's striking this Orioles team out at a 26% clip across 53 at-bats, a sample size we can get behind.

With a heavy right-handed hitting lineup expected to be deployed for Tampa, they'll win this one outright. Play up to 50 cents at Polymarket.

  • Time: 7:05 p.m. ET
  • How to watch: Apple TV

Joe Osborne's expert pick: Diamondbacks -1.5

Price: 40¢ (+150) at Polymarket

There’s an incredible amount of data pointing toward Arizona winning this game comfortably.

Over the past month, the Diamondbacks rank first in home OPS, while the Reds sit at 27th on the road. Both teams will start left-handers, which creates another massive edge for Arizona. The D-backs rank second in OPS against lefties during that span, compared to 28th for Cincinnati. Eduardo Rodriguez also owns an ERA nearly two runs lower than Nick Lodolo, and the Reds’ bullpen has been one of baseball’s worst in recent weeks. Cincinnati is just 4-10 in Lodolo’s starts.

Add it all up, and Arizona is worthy of a plus-money runline wager.

  • Time: 9:40 p.m. ET
  • How to watch: Reds.TV, DBacks.TV

More MLB best bets for today

Pick Odds
PIT ML +206
Read analysis in our Pirates vs. Dodgers predictions
SF/BOS o7.5 +105
Read analysis in our Giants vs. Red Sox predictions
MIL ML -140
Read analysis in our Braves vs. Brewers predictions

Odds are correct at the time of publishing and are subject to change.
Not intended for use in MA.
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Robert Criscola - Covers.com
Betting Analyst

Robert M. Criscola’s road to becoming a Covers publishing editor began with an internship at Metro New York, which eventually turned into a freelance job at MetroBet covering many sports from a wagering angle, including horse racing. He continued to focus on “The Sport of Kings” by writing for shapperdacapper.com, danonymousracing.com, and informer.fanxt.com before joining the team at the TwinSpires Edge in 2019 as a regular contributor and weekend editor. “Crisco” began writing game previews for Covers in 2022 and joined the editing team in 2023.

His best advice for sports bettors? Bet with your head, not over it.

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