PHOENIX — Garrett Whitlock retreated to the Red Sox clubhouse after logging a massive five-out relief effort Sunday, and watched gleefully as his teammates exploded for an unlikely three-run rally to claim a 7-4 advantage in the top of the ninth inning. As he received treatment from the trainers, Whitlock watched the bottom of the ninth with Sox strategy analyst Dave Miller.
With the Red Sox desperate for a win, Miller nervously paced in the visitors’ clubhouse at Chase Field. Whitlock offered a suggestion.
“I was like, ‘Sit down, dude. You’re stressing me out. It’s Chappy. It’s fine,’ ” Whitlock relayed.
Indeed, it was. In the latest addition to his historic season, Aroldis Chapman achieved a career first to seal the Sox’ victory.
After he punched out Blaze Alexander on a slider, Chapman fanned Ildemaro Vargas on a splitter in the dirt that caromed away from catcher Carlos Narváez for a wild pitch. Unperturbed, Chapman fanned Tyler Locklear on a slider before closing out the game with a strikeout of Jordan Lawlar on a splitter.
It marked the first time in Chapman’s prodigious career that he’d struck out four batters in a single frame, and he became the third Red Sox pitcher to do so, joining Craig Kimbrel (2017) and Tim Wakefield (1999). The accomplishment added an exclamation mark to one of the greatest reliever stretches in big league history.
How to describe Chapman’s season?
“Nasty. Bien. Nasty. Nasty,” said Brayan Bello.
“Magical,” said Whitlock.
“He’s a beast,” said Narváez. “[And] he’s at his peak.”
On Sunday, in his 60th game of the year, Chapman lowered his ERA to 0.98 — the lowest of his career, and putting him in the company of just 10 pitchers in big league history with a sub-1 ERA in at least 60 appearances. His 40 percent strikeout rate, while not the highest of his career, is elite, particularly given that he’s been able to attack the strike zone as never before in his 16 big league seasons, with a 7 percent walk rate that is his best ever.
Incredibly, when Vargas reached, it ended a stretch of 21 consecutive batters Chapman had retired. He has gone 17 straight games (14⅔ innings) without allowing a hit, the third-longest streak by games in big league history. Opponents are hitting .113 (technically .1129) against him, which would be the lowest mark by a pitcher with at least 50 innings, surpassing the mark set by Kirby Yates (.1132) last year.
As much as Chapman is renowned for his incredible velocity, his most recent dissection demonstrated the lefthander’s ability to adapt. His sinker sat Sunday at 97.4 miles per hour — somehow, one of his lowest marks of the season — and so he more heavily employed his slider and splitter to great effect.
Chapman’s arsenal has always been unsettlingly diverse for opposing hitters. This year, his command of his entire mix has arrived at another level.
“I always have confidence in those pitches,” said Chapman via translator. “The difference right now is we have been able to control more of those pitches and I have been able to command more.”
Narváez is able to adapt his game plan to the strengths and weaknesses of opposing lineups as well as Chapman’s mix on any given day. With four offerings (four-seamer, sinker, slider, splitter) that elicit whiffs on more than 30 percent of swings, Chapman has been able to dispatch opponents in a fashion rarely witnessed in big league history.
Red Sox manager Alex Cora has seen incredible seasons from closers — including the run of 84 consecutive save opportunities converted by the Dodgers’ Eric Gagne from 2002-04, which encompassed a Cy Young Award in 2003. He suggested Chapman is nearly on a par.
“This is special, let’s put it that way,” said Cora. “To do it at this age and where we’re at as an industry, as far as the hitters and adjustments that they make, it’s eye opening.”
Cora raved about the work ethic and routines that have allowed Chapman to dominate at age 37 — a lift at the beginning of the morning, another when he gets to the park, early-afternoon catch on the field, and then a nap in preparation for the game.
“I love the fact that people here are respecting that and hopefully it rubs off on other guys and they can work the way he does,” said Cora.
For the Red Sox, regardless of his influence on the routines of teammates — which is considerable, adding to the team’s eagerness to sign the reliever to a contract extension covering the 2026 season with a vesting option for 2027 — Chapman’s performance at the end of games has been transformative.
On a contender that is navigating instability in several facets of its roster while trying to get across the finish line and into the postseason, Chapman has offered a constant — one performing at an outrageous level, giving the Sox (67-2 when leading after eight innings) reassurance that leads are likely to turn into victories.
“At one point he’s going to give up a hit. He will,” said Cora. “But let’s enjoy the ride.”
Alex Speier can be reached at alex.speier@globe.com. Follow him @alexspeier.