Arizona Diamondbacks rise in NL West, beating expectations

On the first day of spring training, Diamondbacks General Manager Mike Hazen said that a successful season would involve contending at the trade deadline and playing meaningful baseball in September. With the season having just passed its quarter point, the Diamondbacks are on pace to blow past those expectations.

Their 25-19 record is the sixth best in baseball. Their playoff odds, per Fangraphs, have shot up from 15.3% on Opening Day to 44.4% entering play Friday. No other team in the National League has seen its chances rise more.

So how have the Diamondbacks done it? And can it continue?

The dominance of Zac Gallen (and Merrill Kelly)

It might seem weird to start with pitching, given that the Diamondbacks rank eighth in runs scored and 21st in runs allowed. But it’s impossible to overstate the impact that Zac Gallen has had on this team.

In spring training, Gallen said the names of the 10 voters who did not put him on their Cy Young ballots would “be on a list somewhere.” He might not have to worry about that this year, as he is the current favorite for the award. Before Friday's start against the Pirates went sideways, his 2.35 ERA was third in the National League and his 57.1 innings pitched second. He was on pace for 9.5 WAR, per Fangraphs, which would be the most by a pitcher since Randy Johnson in 2004.

Often, these types of dominant starts involve a touch of overperformance that's unlikely to carry on for a whole season. Not Gallen’s. He’s striking out a career-high 11.0 batters per nine innings and walking a career-low 1.3 batters per nine. Both his four-seam fastball and curveball are getting more whiffs than ever before, while his changeup and cutter are getting more whiffs than they have since 2020. This isn’t a small sample size, either. Gallen has dominated since last August. Over his last 20 starts, his ERA is 1.80.

The result, for the Diamondbacks, is something close to an automatic win when he’s on the mound. There’s a reason they haven’t lost more than three games in a row.

Merrill Kelly has been critical, too, helping alleviate the impact of three rotation spots that have mostly been filled by struggling rookies. In his first three starts, Kelly was lucky to have a sub-3.00 ERA. He was walking a concerning 7.0 batters per nine, something he attributed in part to having his spring training interrupted by the WBC. Since then, he’s down to 2.2 walks per nine, while striking out more than he ever has. The ERA is still excellent at 2.92. Now, it feels legitimate.

With Geraldo Perdomo's breakout, no easy outs

Last year, when the Diamondbacks went 74-88, the bottom of their lineup was putrid. Their 7-9 hitters had the 27th-ranked batting average at .212, with a paltry .603 OPS. This year, those spots rank sixth in average (.254) and 13th in OPS (.694).

That success is largely attributable to Geraldo Perdomo and Gabriel Moreno. Perdomo has been the surprise of the season, hitting .330/.425/.527, something the Diamondbacks attribute to off-season work learning to stay more grounded in his swing. Moreno is hitting .321/.345/.402 and has made all but two of his starts hitting seventh or eighth in the order.

Batted ball data suggests both players are likely to regress when comparing numbers based on quality contact (xwOBA) and numbers based on results (wOBA). That comparison poses the possibility that Perdomo has been the luckiest hitter in baseball. Moreno has also been fairly fortunate, though he is producing above average exit velocity.

There’s another aspect of ‘no easy outs,’ though, that is more replicable. As a team, the Diamondbacks strike out at the fourth-lowest rate in baseball. And after struggling to draw walks for the first three weeks, they’ve been excellent in that category over the past four weeks, now ranking seventh in OBP.

Thanks to Lourdes Gurriel, a more balanced lineup

There was little doubt entering the season that the Diamondbacks would hit right-handed pitching well — and they have. How they would fare against lefties was a bigger question.

Last year, they ranked 26th in OPS against lefties, with a team total of .655. This year, that number is up to .703, just above league average.

What gives? Christian Walker and Ketel Marte have continued to crush lefties, as they always do. Moreno is hitting over .400 against them. Evan Longoria and Emmanuel Rivera have been nice platoon options. But more than anything, the improvement can be attributed to Lourdes Gurriel Jr.

Gurriel came over with Moreno in the off-season trade for Daulton Varsho, billed as a secondary piece in the deal. That may be true in the long-term, with Gurriel a pending free agent and Moreno having five more years of team control. But this year, Gurriel has been every bit as important.

He’s hitting the ball hard 46.7% of the time, more than any other qualified Diamondback, and is whiffing at a career-low 17.4% rate. That combination has helped Gurriel produce the sixth best OPS (.924) in the National League, giving the Diamondbacks a third potent right-handed bat in the middle of their order, along with Walker and Marte.

Excellent clutch hitting

Entering last week’s 10-game homestand, the Diamondbacks were the best team in baseball at hitting with runners in scoring position, making productive outs and scoring runners from third base with less than two outs.

“I think we have a really good approach and a really good mindset when we get guys on,” Manager Torey Lovullo said at the time. “… It's not going for the jackpot every time with runners on. I think you've gotta continue to chip away and be stubborn and hit the ball where it's pitched and having an all-field approach.”

Problem is, hitting with runners in scoring position is heavily luck based. Since Lovullo gave that quote, the Diamondbacks are hitting just .193 with runners in scoring position. Just as their clutch hitting has won them games for much of the season, it’s lost them games in the last week and a half.

From here on out, it’s fair to expect them to hit between those two extremes.

Bringing runners home with productive outs is likely a little more replicable. Because the Diamondbacks don’t strike out much, they’ll always move runners over at a higher rate than teams that do. Whereas their batting average with RISP has dropped to 11th during this stretch, their ability to get runners home from third with less than two outs is still third.

Improved infield defense led by Josh Rojas

In the off-season, much was made of the Diamondbacks' outfield defense, which was by far the best in baseball by Statcast’s outs above average metric last season.

The outfield defense, though, has largely been a disappointment. Varsho was traded, Alek Thomas has struggled relative to defensive expectations and Jake McCarthy was sent down to Triple-A. The replacements, like Gurriel and Pavin Smith, aren’t as good on that side.

The infield defense has made up for it. The Diamondbacks’ infield is on pace to be worth 29 outs above average, up from eight last year. Walker has continued to play the best first base in the league, but the real difference maker has been Josh Rojas. Last year, he graded out as the league’s fourth-worst third baseman. This year, he’s been the third best.

That’s been particularly helpful because Diamondbacks pitchers induce ground balls at an above-average rate, putting pressure on their infield.