Last Updated on July 21, 2025 10:08 am by Anthony Rome
The Houston Astros (57‑42) head west to take on a .500 Arizona Diamondbacks squad (50‑50) in Phoenix tonight at 9:40 p.m. ET. This first game of the series comes with the Diamondbacks slightly favored, and both teams riding contrasting momentum as the trade deadline looms. What’s the best bet in tonight’s Astros vs. Diamondbacks matchup?
Game Matchup & Betting Odds
Houston Astros at Arizona Diamondbacks
9:40 p.m. ET, Monday, July 21, 2025
Chase Field, Phoenix, AZ
Astros vs. Diamondbacks Betting Odds
According to oddsmakers from online sportsbook Bovada.lv, the Diamondbacks are -132 moneyline favorites to beat the Astros, who are +122 moneyline underdogs. The total, meanwhile, is sitting at 9 runs.
Astros vs. Diamondbacks Public Betting: Bettors Leaning Arizona
As of this writing, our MLB Public Betting Page shows that 56% of the bets are on the Diamondbacks moneyline. That said, this page is updated frequently so make sure that you click on the link provided so that you’re getting the most updated information.
Pitching Matchup
Houston will hand the ball to rookie left-hander Colton Gordon (3‑2, 4.67 ERA), hoping he can silence Arizona’s lineup after a rocky stretch in recent outings. Opposite him is Zac Gallen (7‑10, 5.40 ERA), who has struggled this season but posted a strong 32 K’s in early trips vs. the Astros. Both southpaws present windows: Gordon needs to limit free passes, while Gallen hopes to reclaim consistency.
Offensive Firepower
Offensively, the Diamondbacks lead the league in runs per game (5.2) and sit fifth in homers (145). Eugenio Suárez leads with 35 long balls and 85 RBIs, while Geraldo Perdomo (.272, 10 HR, 58 BBs) has surged lately. Arizona rolled into the break winning four straight, riding that offensive tide.
Houston’s lineup has been solid but unspectacular: 4.4 runs per game with 112 homers, batting .258 overall. Rookie standout Jeremy Peña (.322 AVG, 11 HR) anchors the offense, while Yainer Díaz offers pop with 13 homers.
Astros vs. Diamondbacks MLB BETTING PREDICTION
This opener appears destined for a slugfest. Both starters have been hittable, and with offensive depth on display, the bullpens will likely be leveraged early. Arizona’s lineup could get on the board quickly, but Houston isn’t far behind—Gordon must eat innings to reduce strain on his relief corps, while Gallen needs a bounce-back to quiet the Astros hitters. With both clubs prone to run-scoring bursts, timing and bullpen management will be crucial.
Astros vs. Diamondbacks MLB Playoffs Prediction: OVER 9