The Diamondbacks earned their rest Monday after a weekend sweep in Philadelphia that improved their record to 44-26, the best 70-game start in franchise history. They lost on Tuesday in the opener of a three-game series in Colorado; before that game, the Diamondbacks had a 3.44 earned run average, ranking second in the majors. Last season it was 5.09, the highest.
Pitching has vaulted Arizona into a blistering National League West pennant race with the Rockies (47-26) and the Los Angeles Dodgers (45-26), who are trying to win their fifth straight division title. It is a sudden reversal for the Diamondbacks, who sagged to 93 losses last season and fired General Manager Dave Stewart and Manager Chip Hale.
Mike Hazen, who had been the general manager of the Boston Red Sox, took over in October and inherited perhaps the most bizarre salary situation in the game. The team’s ace, Zack Greinke, has the highest average annual salary in the majors, at more than $34 million. That consumes more than a third of the overall payroll for the Diamondbacks, who will pay nobody else more than $9.5 million this season.
When Hazen sought to replace the free-agent catcher Welington Castillo, he figured he could give Lovullo flexibility by looking for two catchers, specifically those who could deftly handle a staff, while retaining the versatile Herrmann. He found Mathis for two years and $4 million, and Iannetta for one year and $1.5 million.
“Their reputation preceded them for what they’ve brought to teams,” Hazen said. “So when we changed the direction on the model that we were looking at, on how to put that catching situation together, those guys stood out to us.”
Hazen traded the N.L. hits leader, shortstop Jean Segura, to Seattle for starter Taijuan Walker, a 24-year-old right-hander with a middling record but enticing potential. Iannetta caught Walker with the Mariners and had seen him begin to morph his cutter into a slider, a slower pitch that can further differentiate from his fastball.
The pitch has helped Walker to a 3.32 E.R.A., the best of his career. It reminded Iannetta of a similar process with Ubaldo Jimenez, whom he caught in Colorado, when Jimenez was an All-Star.
“It took Ubaldo about a year to really get a feel of it, and that’s kind of the path that Tai’s been on,” Iannetta said. “His ability to command the zone and really being able to use that slider has given him a huge advantage.”
Greinke, who missed six weeks with an oblique injury last season, has sliced his E.R.A. from 4.37 last year to 3.14 this year. Greinke works exclusively with Mathis and has benefited from preparing with Dan Haren, the former All-Star and the Diamondbacks’ new pitching strategist.
Hazen said he never doubted Greinke, even though his average fastball velocity has fallen to 90.8 miles per hour, its lowest point in 12 years, according to FanGraphs.
“When we got to spring training, everybody was talking about velocity — but Zack’s never been an elite velocity guy,” Hazen said. “He’s been one of the best command pitchers in baseball for the entirety of his career. And he’s as smart as everybody says he is.”
The left-hander Robbie Ray has been another ace for Arizona, after a 2016 season that was nearly unprecedented for its pairing of dominance and dismay. Ray had 218 strikeouts with a 4.90 E.R.A., making him just the second pitcher ever with so many strikeouts coupled with such a high E.R.A. The other was Bobo Newsom of the 1938 St. Louis Browns, who had 226 strikeouts to go along with a 5.08 E.R.A.
Ray’s fastball averages 94.1 m.p.h., second only to Boston’s Chris Sale among qualified left-handers, and he is in the top five in the National League in strikeouts and E.R.A. The difference this season, besides an improved tempo, is his use of the curveball. Ray throws fewer fastballs, changeups and sliders this season, but nearly a quarter of his pitches have been curveballs, compared to just 5.3 percent in 2016.
“If guys are on the heater with guys on base or something, you want to go, go, go, go,” Ray said. “The curveball allows me to kind of back off a little bit.”
Lovullo has paired Ray with Herrmann lately, while Zack Godley has pitched mostly to Iannetta. Godley has been sharp after struggling last season, as has Archie Bradley, who has grown from an uneven starter to a dominant setup man for closer Fernando Rodney. Bradley credited the catchers for the staff’s improvement.
“You can go into pitch framing and all the stuff they do really well, but it starts, at least for me, with the relationship,” Bradley said. “All three guys, Iannetta, Mathis and Herrmann, they understand us, man. They understand the way our balls move, they understand where we like them to set up, everything. When we step on the mound, there’s no doubt.”
The Diamondbacks have won without Shelby Miller, who needed Tommy John surgery after four starts. The team acquired Miller from Atlanta before last season, surrendering two young players who now start for the Braves: center fielder Ender Inciarte and shortstop Dansby Swanson.
It was a costly deal, but the Diamondbacks just might overcome it. They retain a deep lineup, led by first baseman Paul Goldschmidt, an all-around force who could be the N.L.’s most valuable player so far, hitting .324 with 17 homers, 58 runs batted in and 13 steals to go along with his usual stellar defense. Third baseman Jake Lamb also has 16 homers, and three other regulars are hitting above .290.
Then there are the catchers. They have combined for 15 homers, the most for any N.L. team’s catchers. Their .187 average before Tuesday ranked last, but nobody is complaining. The catchers seek one another’s input during games, and the pitchers skillfully follow their advice.
For Mathis, that means everything. He once bruised the Yankees for five doubles in a playoff series, but otherwise has been a marginal hitter, with a .159 average now. He said he had never forgotten the words of his first major league manager, the Angels’ Mike Scioscia, who told him he could last a long time by mastering the nuances of life behind the plate.
It was sound advice, and it also applies to Iannetta, a career .229 hitter. They have survived, and when their pitchers thrive, they have done their jobs.
“That’s the most important part of it for me,” Mathis said. “You want to hit and do things offensively to help the team out, but what I’ve enjoyed over the years is working with pitchers, trying to understand them and get them where they need to be.”
The Diamondbacks’ pitchers are there now, with a turnaround that started from 60 feet 6 inches away.