Invisible Insider
July 21, 2025
Game Preview
Astros at Diamondbacks MLB Betting Preview

Game Time: 7/21, 09:40PM

1. Brief Intro

The Houston Astros will face off against the Arizona Diamondbacks in a compelling matchup under the Friday night lights. DraftKings lists the Diamondbacks as a -151 favorite with the Astros as a +124 underdog, and a substantial 86% of bettors are backing Arizona. With key pitching duels and lineup dynamics at play, this game offers intriguing angles for bettors to consider.

2. Pitcher Breakdown

Pitching Matchup: Colton Gordon vs. Zac Gallen
Colton Gordon (HOU):

Colton Gordon features a diverse arsenal: Four-Seam (39% usage, 91.3 mph); Sweeper (31% usage, 80.4 mph); Sinker (12% usage, 91.6 mph); Curveball (12% usage, 76.0 mph); Changeup (6% usage, 84.4 mph). Gordon's mix leans towards finesse with a balance of breaking and off-speed pitches. The Diamondbacks lineup has a season average of .259 with a projected xBA of .239 against Gordon's offerings.

Zac Gallen (AZ):

Zac Gallen's repertoire includes a Four-Seam (48% usage, 93.3 mph); Curveball (24% usage, 81.0 mph); Changeup (14% usage, 86.8 mph); Slider (7% usage, 87.6 mph); Cutter (6% usage, 89.3 mph); Sinker (1% usage, 93.3 mph). Gallen's velocity and variety pose significant challenges, with the Astros lineup averaging .261 this season but projecting to .224 against Gallen's arsenal.

3. Lineup Advantage vs. Arsenal

Lineup Matchups & Batting Edges
For Away Team vs. Home Pitcher:

The Astros lineup's season average is .261, projecting to .224 against Gallen. Notable performance changes include Cam Smith: Season BA .323 → xBA .264 (-59 points), Season K% 17.7% → Arsenal K% 23.9% (+6.2%). Taylor Trammell's projected xBA decreases significantly: Season BA .250 → xBA .159 (-91 points), Season K% 22.5% → Arsenal K% 51.3% (+28.8%).

For Home Team vs. Away Pitcher:

The Diamondbacks lineup averages .260 this season, projecting to .239 against Gordon. Josh Naylor sees a notable dip: Season BA .292 → xBA .234 (-58 points), Season K% 12.3% → Arsenal K% 24.5% (+12.2%). Alek Thomas's xBA drops: Season BA .246 → xBA .170 (-76 points), Season K% 26.4% → Arsenal K% 31.8% (+5.4%).

4. Lineup Strikeout Trends vs. Arsenal

Strikeout Risks & Rewards

The Astros' projected K-rate is 26.7% vs. Gallen — up 6.0% from their 20.7% season average. This suggests potential value in Gallen's strikeout prop. Meanwhile, the Diamondbacks' projected K-rate is 25.7% vs. Gordon — up 6.1% from their 19.5% season average, indicating a similar strikeout opportunity for Gordon.

5. Umpire Influence

Behind the Plate: TBA

Umpire assignment has not been announced, which makes prop volatility a concern.

6. Betting Interpretation / Final Lean

Final Lean & Betting Takeaway

STEP-BY-STEP BETTING ANALYSIS:

STEP 1: Check ALL individual batters for prop opportunities
Upon reviewing the key performers, no batter meets the criteria of an xBA over .300 with a boost greater than +20 points. Therefore, no batting leans are suggested.

STEP 2: Check team strikeout rates for pitcher props
Both teams show a significant increase in strikeout projections. The Astros' projected K-rate of 26.7% and the Diamondbacks' 25.7% both exceed the 25% threshold with increases over 4%. This suggests leaning towards the strikeout OVER props for both Gallen and Gordon.

STEP 3: Report findings
Our final lean would be Zac Gallen strikeout OVER - Houston's projected K-rate jumps to 26.7% vs. Gallen, up 6.0% from their 20.7% season average. Similarly, Colton Gordon strikeout OVER is a strong consideration given Arizona's projected K-rate of 25.7%, up 6.1% from their 19.5% season average.

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