Cubs vs. Diamondbacks Prediction: Chicago’s Depth Advantage Shows in Phoenix

The Cubs have owned the Diamondbacks all season, and Arizona's depleted rotation makes tonight's series opener at Chase Field no different. Our prediction and best bet.

Andrew Elmquist August 24, 2026

The Cubs have owned this matchup all year, but the Diamondbacks are the ones playing for something bigger right now.

Quick take:
Pick: Chicago Cubs -1.5
Why: Arizona is without three of its top four rotation arms, and Chicago just dropped 19 runs on Seattle a day earlier
The number to watch: Cubs lead the season series 3-0

Chicago rolls into Chase Field at 75-56, sitting second in the NL Central and firmly in control of a National League Wild Card spot with a four-game cushion. Arizona, at 69-62, is fighting from the other direction — two games back of the final Wild Card slot and trying to salvage a season that’s slipped further away with each rotation injury. The Cubs took the first three meetings between these clubs back in early May, all by multiple runs, and arrive in Phoenix a much healthier, deeper team than the one they’re facing tonight.

Monday’s opener kicks off a three-game set that could shape both teams’ final six weeks. Chicago is 13-9 in August and just posted a 19-2 blowout of the Mariners on Sunday, with Ian Happ and Pedro Ramírez each driving in five runs. Arizona won its last two of three against Cincinnati but has needed every bit of offense to cover for a rotation that’s been gutted by injury.

Why the Market Still Trusts Chicago on the Road

Books opened this one with Chicago around -131 and the number has crept to as high as -150 by first pitch, with the total sitting near 9. That line movement tells the story: Kevin Gausman gets the ball for the Cubs at 6-11 with a 4.58 ERA, numbers that undersell how much run support and bullpen stability sit behind him, while Arizona counters with Merrill Kelly at 8-11 and a 5.37 ERA that’s been trending the wrong way. Neither starter is inspiring confidence, which is part of why the total has stayed near double digits and why sharp money has leaned toward the side with the deeper roster rather than either arm. Anyone still shopping for a DraftKings promo code before placing a bet on this series has time before Monday’s first pitch.

A Rotation Running on Fumes in the Desert

Arizona’s pitching depth has been stripped bare over the past six weeks. Zac Gallen and Corbin Burnes are both out until at least early September with elbow issues, Ryne Nelson has been shut down since mid-June, and the bullpen just lost Ryan Thompson to a back injury. That leaves Merrill Kelly and Brandon Pfaadt carrying a heavier workload than the Diamondbacks would like against a Cubs lineup that’s hitting .250 as a team with 174 home runs, both marks ahead of Arizona’s .245 and 129 long balls. Chicago’s offense has also been red-hot lately, riding a four-game stretch of at least five runs entering this series.

The lineup card doesn’t help Arizona’s cause either. Ketel Marte, arguably the Diamondbacks’ most important hitter, has been out since mid-August with knee inflammation and has no firm timetable to return. Lourdes Gurriel Jr. is only just working his way back from a groin strain, and Tommy Troy remains sidelined with a shoulder issue. Arizona has scored at least five runs in four straight games, so the bats haven’t gone cold entirely — but replacing Marte’s on-base ability in the middle of a playoff race is not a small thing.

Other Game Picks

Chicago has beaten Arizona by an average of nearly five runs across the first three meetings this season.

That gap matters more than a simple 3-0 season-series record suggests. It reflects a talent and depth disparity that’s only widened since May, with the Diamondbacks now missing multiple frontline starters and a middle-of-the-order bat. Chicago, by contrast, is 76-55 in its expected-record profile per run differential — actually a touch better than its literal record — which suggests this isn’t a team riding good luck. If you’re weighing where to put a wager down on this series, the market’s respect for Chicago’s -1.5 number lines up with what the underlying numbers say.

Kevin Gausman isn’t dominant right now, but he doesn’t need to be against a lineup missing its best on-base threat.

Park factors are also worth a mention here. Chase Field has played as a hitter-friendly environment for most of this season, which is part of why the total sits close to 9 despite two shaky starters. That cuts both ways for bettors: it raises the ceiling on a Cubs offense that’s already scoring at a top-tier clip, but it also means Arizona’s lineup, even shorthanded, has a puncher’s chance to keep games within reach late. Anyone shopping lines before placing a bet should note that total carries plenty of variance in this ballpark, even if the side feels more predictable.

Prediction and Best Bet

Chicago’s rotation, bullpen, and lineup all hold clear edges over an Arizona club that’s been forced to piece things together in the second half. The Cubs have already proven they can beat this roster convincingly, and nothing about Arizona’s health situation has improved since May.