Guardians vs. Diamondbacks Prediction, Odds, Probable Pitchers and Prop Bets for Wednesday, Aug. 20

Parker Messick will make his MLB debut for the Guardians on Wednesday.

Parker Messick is an underdog in his MLB debut. / Brett Davis-Imagn Images

The Cleveland Guardians have split the first two games of their early-week series with the Arizona Diamondbacks, but they are 9.5 games out of first place in the AL Central and fading fast in the wild card race.

On Wednesday, the Guardians will turn to former second-round pick Parker Messick, who is making his MLB debut. Messick posted a 3.47 ERA in Triple-A so far this season, striking out 119 batters in 98.2 innings of work.

He’ll take on Arizona righty Brandon Pfaadt, who has struggled mightily in the 2025 season, posting a 5.08 ERA while ranking in the bottom three percentile in expected ERA and expected batting average against amongst all MLB pitchers.

Can Messick lead the Guardians to a win on Wednesday afternoon and help them potentially pick up a game in the AL wild card standings?

Here’s a breakdown of the odds, players to watch in the prop market and my prediction for this series finale. 

Guardians vs. Diamondbacks Odds, Run Line and Total

Odds via DraftKings Sportsbook

Run Line

• Guardians +1.5 (-194)
• Diamondbacks -1.5 (+157)

Moneyline

• Guardians: +104
• Diamondbacks: -126

Total

• 9 (Over -108/Under -112)

Guardians vs. Diamondbacks Probable Pitchers

• Cleveland: Parker Messick (making MLB debut)
• Arizona: Brandon Pfaadt (12-8, 5.08 ERA)

Guardians vs. Diamondbacks How to Watch

• Date: Wednesday, Aug. 20
• Time: 3:40 p.m. EST
• Venue: Chase Field
• How to Watch (TV): ARID, CLEG
• Guardians record: 64-61
• Diamondbacks record: 61-66

Guardians vs. Diamondbacks Best MLB Prop Bets

Guardians Best MLB Prop Bet

• Jose Ramirez to Hit a Home Run (+425)

Earlier today, I shared in SI Betting’s best home run picks – Daily Dinger – why Ramirez is a great bet to go deep for the second game in a row: 

Cleveland Guardians star Jose Ramirez went deep on Tuesday against the Arizona Diamondbacks – his 26th home run of the 2025 season.

I’m betting on him to leave the yard once again on Wednesday afternoon, as he takes on D-Backs righty Brandon Pfaadt, who enters this start with a 5.08 ERA and 21 home runs allowed in 25 appearances.

Pfaadt ranks in just the third percentile amongst MLB pitchers in expected ERA and the second percentile in expected batting average against. That sets up well for Ramirez, who is hitting over .300 over the last seven days. On top of that, Ramirez has been great against right-handed pitching this season, hitting 21 home runs while posting an OPS just south of .900. 

He’s a great bet at this price on Wednesday afternoon. 

Guardians vs. Diamondbacks Prediction and Pick

Messick is entering an interesting spot, as the D-Backs are 12th in MLB in batting average against left-handed pitching this season, but they gutted their lineup with multiple deadline trades. 

So, the rookie may actually have a chance to put together a strong debut for a Guardians team that is still in the playoff hunt.

Meanwhile, Pfaadt is looking to close the season on a high note, because there hasn’t been much to get excited about to this point in 2025. I mentioned his terrible advanced numbers earlier, but Pfaadt’s actual ERA, WHIP and other numbers are equally as bad.

He’s posted a 1.36 WHIP this season, allowing 151 hits in 133.0 innings of work, and he has allowed at least three runs in 15 of his 25 outings.

Arizona is just .500 at home this season, and the Guardians are shockingly better on the road (33-30) than they are at home (31-31) in 2025. 

I’ll take a chance on Cleveland to pull off the upset in Messick’s debut. 

Pick: Guardians Moneyline (+104 at DraftKings)

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Odds refresh periodically and are subject to change.

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