Houston Astros vs. Arizona Diamondbacks: Predictions, Odds, Best Bets, Starting Lineups (9/29/23)

The Arizona Diamondbacks host the Houston Astros for the first game of a three-game series Friday night (9/29/23). Both teams are battling for playoff position as they enter the final weekend of the regular season.

With ace Zac Gallen on the mound, the Diamondbacks are the betting favorites at -130 on the moneyline, while the over/under is set at 8.5 runs. Continue below for the Astros vs. Diamondbacks prediction and best bet recommendation that the Diamondbacks will win.

Astros vs. Diamondbacks Prediction

Starting pitchers: RHP J.P. France (11-6, 3.83 ERA) vs. RHP Zac Gallen (17-8, 3.49 ERA)

It’s not often you have an interleague matchup in September with a playoff feel to it, but that is exactly the case in this series with so much at stake for both teams. Both the Astros and Diamondbacks could still finish in the 2nd Wild Card spot in their respective leagues, but they also could still miss the playoffs entirely.

The Astros are currently 1 game back of Toronto for the 2nd Wild Card spot in the American League, and they have a 1-game lead on Seattle for the final playoff spot. Both Toronto and Seattle own tiebreakers over Houston, so the Astros’ magic number to clinch the playoffs is 3 (i.e. they need some combination of wins and Mariners losses to add up to 3 in order to clinch).

There is even a scenario where the Astros (or the Mariners) could still win the AL West and earn a bye during the Wild Card rounds if Seattle wins at least 2 of the next 3 against Texas. If Seattle wins at least 2 and Houston wins all 3, then the Astros would win the AL West because they own the tiebreaker over Texas. If Seattle wins all 3 against Texas, and Houston wins exactly 2 games, it would be a crazy scenario with all 3 AL West teams tied with 89 wins, and Seattle would win the division.

The Diamondbacks have a 1.5-game cushion on the 2nd Wild Card spot in the National League, but both the Cubs and the Marlins are in striking distance to overtake them and potentially push them out of the playoffs entirely. They own the tiebreaker over the Cubs, so 1 win would clinch a playoff spot. They do not own the tiebreaker against Miami, so they need a combination of 3 wins and/or Miami losses to clinch the 2nd Wild Card spot.

The Diamondbacks must feel good about their chances in tonight’s game with their ace Zac Gallen on the mound. Gallen was considered a Cy Young contender for much of the season, but fell out of contention with a 4.11 ERA since the All-Star break including a 4.45 mark in September.

It’s been hit-or-miss for Gallen this month (no pun intended), as he has two scoreless outings including a complete game shutout of the Cubs, but gave up at least 4 runs and lasted no more than 5-1/3 innings in his other three starts. The Diamondbacks need more outings like the former and fewer of the latter in this most critical stretch of the season, especially with such a tough matchup tonight.

Houston has been one of the best offenses in the majors all season and they have been especially strong over the last month. They are 5th in the league in average (.269), 2nd in OPS (.833) and wOBA (.355) and 1st in wRC+ (128) during September. They have been even better against righties this month, averaging .291 with an .884 OPS, .375 wOBA and 142 wRC+. They lead the league in all those categories.

By contrast, Arizona has been middle-of-the-pack offensively for most of the season, including this month. They have struggled more against righties during September, averaging .321 with a .689 OPS and .303 wOBA. Those marks all fall in the bottom 7 in the league over that span.

Thankfully for the Diamondbacks they have an easier pitching matchup against Astros rookie J.P. France, at least on paper. France has had a very solid rookie season but has started to struggle over his last 6 starts when he has a 7.94 ERA and a 1.91 WHIP. Those numbers are a bit skewed by 1 terrible outing Boston, when he last only 2-1/3 innings and allowed 10 earned on 11 hits. But even without that outing, he still has a 5.19 ERA and 1.58 WHIP over his last 5.

Despite their struggles against righties this month, Arizona still has plenty of pop to get after a pitcher like France, and Gallen is certainly capable of keeping the Astros’ potent bats at bay. However, Houston is the far more experienced lineup given all their recent playoff success, and they have also been an excellent road team this season with a 48-30 record.

Games like this tend to come down to pitching, and Arizona not only has the superior starter but also has been better in the bullpen recently (discussed further below). For those reasons we recommend betting on the Diamondbacks to take the first game of this series.

Astros vs. Diamondbacks Prediction: Diamondbacks moneyline (-130)

Astros vs. Diamondbacks Odds

The Diamondbacks are the betting favorites at -130 on the moneyline, while the Astros’ moneyline odds are +110.

The Diamondbacks are laying -1.5 runs on the spread at +154 odds, while the Astros are getting +1.5 runs at -185 odds.

The over/under in this game is set at 8.5 runs with -118 odds on the over and -102 odds on the under.

Astros vs. Diamondbacks Key Matchups

Here are the key matchups that could decide Astros vs. Diamondbacks.

J.P. France vs. playoff atmosphere
The biggest reason we picked the Diamondbacks in our Astros vs. Diamondbacks prediction is the advantage they have on the mound with a veteran ace like Zac Gallen against a rookie like J.P. France.

We detailed France’s recent decline earlier, but it’s worth mentioning that this is by far the biggest game France has ever pitched in with the playoffs on the line against a playoff-caliber opponent. Unlike the rest of the Astros’ roster, France has never pitched in the postseason or in a high-stakes game of this magnitude at this level.

Some pitchers rise to the occasion in moments like that and others fold under the pressure. We don’t know which one France is but given his recent performance it’s hard to put much trust in him until we see it. Maybe that will happen tonight, and if it does the Astros’ super offense and experience could swing the game in their favor.

Bullpen battle
The Diamondbacks’ bullpen has been finding its groove at the perfect time. While they are just 17th on the season with a 4.28 bullpen ERA and .240 average against, since September 1 they are 3rd in the league with a 2.29 ERA and .202 average against. They have also stranded a league-high 84.9% of baserunners this month.

That success may be a bit unsustainable, as their advanced metrics like FIP and xFIP are closer to their season-long averages, but you can’t argue with the results.

That gives Arizona a slight advantage in this game, but only a slight one as Houston has also been one of the best bullpens all season. Their 3.61 bullpen ERA is 6th in the league this season, and their 3.07 mark this month is also 6th.

Tensions will be sky high if this game comes down to the final outs and the bullpens could end up deciding not only the outcome of this game but also the final playoff standings.

Astros vs. Diamondbacks Starting Lineups (Projected)

Astros Starting Lineup
2B Jose Altuve (R)
3B Alex Bregman (R)
DH Yordan Alvarez (L)
RF Kyle Tucker (L)
1B Jose Abreu (R)
LF Chas McCormick (R)
SS Jeremy Pena (R)
CF Mauricia Dubon (R)
C Martin Maldonado (R)

Diamondbacks Starting Lineup
2B Ketel Marte (S)
RF Corbin Carroll (L)
DH Tommy Pham (R)
1B Christian Walker (R)
LF Lourdes Gurriel Jr. (R)
CF Jake McCarthy (L)
3B Emmanuel Rivera (R)
SS Geraldo Perdomo (S)
C Gabriel Moreno (R)

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Noah hails from Philadelphia and is a diehard Philly sports fan. He graduated from Penn where he was a sports writer and editor for the student newspaper and also spent a summer covering the Baltimore Orioles for MLB.com. He has been playing fantasy sports since before live stats were a thing, and he has enjoyed learning the nuances of DFS in recent years. As a current resident of Florida, he is hoping the wave of sports betting legalization will eventually reach his home state.

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