MLB playoffs 2023: 7 things that will decide the NLCS between the Philadelphia Phillies and Arizona Diamondbacks

From Trea Turner to Corbin Carroll, here's what to watch as the Phillies and Diamondbacks duel for the NL pennant and a ticket to the World Series

Raise your hand if you had this series in your bracket. No? OK, all the more reason to take a step back from the surprises of the past two weeks and dive into the matchup that will decide the National League pennant and one World Series berth.

Not that regular-season records hold much sway this month, obviously, but the 90-win Philadelphia Phillies enter as the favorites and the more likely of the two teams to have arrived at the NLCS. Reprising their 2022, in a way, the Phillies started slowly, then proceeded to go 65-42 from June 1 onward, a 98-win pace. Having dispatched the Miami Marlins and taken down the Atlanta Braves for the second straight year, the Phillies now have their sights set on a second straight pennant.

They will take on the Arizona Diamondbacks, a youthful team just two years removed from losing 110 games. Arizona did something approaching the opposite of the Phillies this season. The D-backs flew out of the gate, going 41-25 and building a four-game lead in the NL West as of June 12. Then they struggled mightily in July and August before righting the ship just enough to earn a playoff spot that guaranteed 2023 would be remembered as a success. Now, suddenly, there are bigger fish to fry. After toppling the Milwaukee Brewers and dismantling the Los Angeles Dodgers, the Diamondbacks are four wins from the franchise’s second World Series appearance.

Whether this is the NLCS you expected is immaterial at this point. It’s time to break down seven factors that will determine who moves on to the World Series.

1. Can anyone get Bryce Harper and Trea Turner out?

As most anyone could tell you, Harper has thrived in the postseason with the Phillies. The past two Octobers, he is batting .354/.448/.768 with nine homers — seemingly all of which have become earth-shaking moments.

This year, though, he hasn’t been the best hitter on his own team. The Phillies’ newest $300 million man, shortstop Trea Turner, is batting .500 in his 26 postseason plate appearances thus far in 2023, with two homers and four steals.

Navigating the Phillies lineup is difficult beyond Harper and Turner — as Nick Castellanos and his four homers in two nights will attest — but the No. 2 and No. 3 hitters in manager Rob Thomson’s lineup present the most acute, most stressful challenge. Beating Philadelphia will almost certainly require finding a way to limit at least one of them.

2. Introducing: Corbin Carroll

Speaking of the postseason’s best hitters, Arizona has one. Year-round baseball fans are no doubt familiar with the Diamondbacks’ right fielder, who sprinted from high schooler to top prospect to franchise player and NL Rookie of the Year favorite in a matter of four years. An action-packed 5-foot-10, Carroll ripped 25 homers and stole 54 bases in the regular season, and he has gone supernova in these playoffs, posting a .412/.565/.824 line with two homers and two steals.

The avatar of the D-backs, Carroll is a threat to wow you at any moment. He packs surprising pop and brilliant speed with a penchant for using his wheels aggressively. In any tight game, watch for Carroll to make a difference as a pest and general chaos agent on the bases.

3. Is there more power where that came from for the Diamondbacks?

Last we saw the Diamondbacks, they were shredding the Dodgers’ Lance Lynn with the first four-homer inning in postseason history. That is … not representative of how the D-backs won during the season, but it might be their best chance at pulling yet another upset.

Arizona finished 22nd in MLB in homers but scored with a combination of contact hitting (fourth-best strikeout percentage) and speed (second in steals). Those skills are very much still present, and the D-backs’ acumen against velocity could be especially useful against the high-octane Phillies bullpen, but homers have been vital to postseason offense in recent seasons, as the level of pitching makes it more and more difficult to string together positive plate appearances.

In the NLCS, young catcher Gabriel Moreno, who has battled through both a head injury and a hand injury this month, could be one to watch. He has already smoked three home runs this month. Christian Walker and Ketel Marte are also legitimate power threats who have posted terrific lines thus far in the playoffs.

Then there are the cherries on top. Speedy center fielder Alek Thomas, who looks like he could be a Corbin Carroll stunt double, has ripped two homers in five postseason games, despite managing only 17 in 238 career regular-season games. And defense-first shortstop Geraldo Perdomo, the MLB leader in sacrifice bunts, started the Game 3 power party against the Dodgers. If Thomas and Perdomo keep homering, the D-backs will probably keep winning.

4. Will Zac Gallen and Merrill Kelly be able to match Zack Wheeler and Aaron Nola?

The Phillies’ one-two punch of Zack Wheeler and Aaron Nola has been proven to work — regular season, postseason, whenever. Their reputations precede them, and for good reason. The Diamondbacks’ top starters aren’t as famous, but they have been just about as good this season.

Zac Gallen, likely to finish top-five for the NL Cy Young for the second straight season, is both a strikeout monster and a workhorse. He finished second in MLB with 210 innings in 2023 while also ranking in the top 10 in K-BB% among qualified starters. Frankly, a lot of his numbers are nearly identical to those of … Zack Wheeler. As an added storyline, Gallen, a South Jersey native, will be pitching the biggest games of his career against his hometown team.

Merrill Kelly, a late-bloomer who found himself in the KBO before making his big-league debut in 2019 at age 30, found a velo boost ahead of 2022 and has been one of baseball’s steadiest starters. The right-hander’s best pitch is a changeup that he commands perfectly and uses liberally, repeatedly fooling hitters by dropping it out of the bottom of the zone.

Slated for Games 1 and 2, thanks to their tidy work against the Dodgers, Gallen and Kelly will be crucial to the D-backs’ hopes of stealing a game in Philadelphia and swinging the odds of the series toward Arizona.

5. Does the crowd really make Philly special?

If you’ve watched a second of this postseason, you’ve already heard the Philadelphia crowd. Citizens Bank Park has been a cauldron of enthusiastic mayhem. From singing Bryson Stott’s walk-up song to the hush-to-hooray uproar of Johan Rojas’ huge catch, the Philadelphia faithful have been a story unto themselves.

It’s very possible the Phillies do have baseball’s best home-field advantage. They’re 10-2 at home the past two postseasons, with both of those losses coming at the hands of the Astros — one of them a no-hitter started by Cristian Javier. So consider this an amplifier to the potentially pivotal roles of Gallen and Kelly. Arizona getting ahead early and/or keeping the Phillies' offense at bay could have a magnifying effect in at least muffling the roar at CBP.

6. Which manager will be more aggressive with his bullpen?

Phillies skipper Rob Thomson has proven to be a decisive and proactive manager of his pitching staff in October. Especially in games in which Wheeler and Nola don’t pitch, he will move quickly to a deep bullpen and turn to his best arms in the biggest moments. He did that in the Phillies’ Game 1 NLDS victory over the Braves and then turned to Craig Kimbrel in a nail-biting, seventh-inning jam in the clinching Game 4.

D-backs manager Torey Lovullo has fewer proven arms to work with, but he might be even more pressed to spread the load across his bullpen. Behind Gallen and Kelly, the D-backs have gotten good work from rookie Brandon Pfaadt but aren’t likely to trust him or any other starter beyond twice through the order. At some point, they will probably have to move even more aggressively to keep up with the Phillies.

The D-backs’ best relievers are Kevin Ginkel and closer Paul Sewald, who was added at the deadline. Former Rays staple Ryan Thompson has also emerged as a weapon for Lovullo, pitching to a 0.69 ERA in 13 games for the D-backs after Tampa Bay released him midseason. The key arms, though, might be left-handers Joe Mantiply and rookie Andrew Saalfrank. They will likely form Arizona’s task force to get Harper out in the middle and late innings.

7. Trea Turner vs. Gabriel Moreno

The running game, with new rules boosting steals and attempts, hasn’t been a huge piece of the storyline thus far in the postseason, but this series could change that.

Turner, who set an MLB record by stealing 30 bases without being caught in the regular season, will have to run against Moreno, who was by far MLB’s most effective thrower from behind the plate, cutting down almost 50% of runners when the league-wide stealing success rate was 80%.

Now, the odds still favor Turner being able to run, but Moreno’s aptitude could provide the D-backs a boost as a deterrent — or a thrill if he gets a chance to become the first to catch Turner.

NLCS prediction:

Despite optimistically (and correctly!) picking the Diamondbacks to make the playoffs before the season started, I have short-changed them this month, failing to foresee their double-whammy of upsets. This time, I still can’t convince myself that Arizona’s ahead-of-schedule 2023 roster stacks up with Philadelphia’s star-studded October machine, but I won’t doubt their ability to compete. Phillies in six.