Yankees relief pitcher Aroldis Chapman walks to the dugout after...

Yankees relief pitcher Aroldis Chapman walks to the dugout after the top of the seventh inning against the Mariners in an MLB game at Yankee Stadium on Monday. Credit: Kathleen Malone-Van Dyke

ST. LOUIS — Understand this first:

No, Aroldis Chapman hasn’t supplanted Clay Holmes as the Yankees' closer.

But the lefthander — a closer from 2012 until earlier this season, when he lost the job to Holmes because of his ineffectiveness combined with the latter’s dominance — seemingly has worked his way back into the Yankees’ circle of trust when it comes to high-leverage situations.

Aaron Boone, who managed Friday night the way he might in October — using Holmes to face the heart of the Cardinals' order in the eighth inning — disclosed after the 4-3 loss that Chapman would have been his closer if Holmes had held the 3-2 lead with which he began the inning.  (Holmes allowed an infield single, a walk and a two-out, two-run double that swung the game in the Cardinals' favor.)

That Boone was planning to use Chapman in the ninth is a reflection of his bullpen not being the finely tuned machine the last month-plus that it had been during the first three months of the season. Scott Effross and Lou Trivino were added before last Tuesday’s deadline as a result.

But it  also was an indication that the Yankees believe Chapman may be on his way to fixing the issues that caused him to lose the closer’s job.

The primary issue? Chapman regaining trust in what has always been his bread-and-butter pitch — the fastball.  

“That’s part of it,” Boone said Friday. “Hopefully we all get rolling like we’re capable of. Chappy’s obviously building momentum.”

Chapman missed 35 games from May 24-June 30 with left Achilles tendinitis. After returning from the injured list July 1 — and walking all three batters he faced July 2 in Cleveland — he has shown signs of being the pitcher he was as a seven-time All-Star.

Though still with a 4.81 ERA in 29 games this season, Chapman came into Saturday night with four straight scoreless outings, allowing one hit and zero walks with five strikeouts in four innings.

“He’s throwing his fastball for strikes again,” Boone said after the third of those outings, a perfect sixth inning July 30 against the Royals in which he struck out two of the three batters he faced in an 8-2 victory. “I think it’s delivery-related, I think it’s focus-related. Not that he’s not focused, but just focused on being efficient with his delivery . . . The fastball, it’s crispy, and I think that’s because he’s efficient with his delivery. Strikes are falling and then his secondary [stuff] can work off of that. I thought again he was really sharp.”

He has done that by relying more on his fastball rather than becoming overly reliant on his slider and splitter, an issue raised by rival scouts and talent evaluators as well as the Yankees behind the scenes.

“Thank God for that,” Chapman said recently through his interpreter. “It [the fastball] has been much better. I’ve been able to spot it and use it more often.”

Before Saturday night’s game, Boone said he continues to be encouraged by what he’s seen from Chapman’s use of the pitch and its effectiveness.

“It’s all related to being more delivery-efficient and being able to repeat his delivery more,” he said. “When he does that, he’s got the more consistent life on it and, not that velocity’s everything, but the velocity has been more consistently in line with who he is [high 90s and reaching 100 mph with regularity]. But command of the fastball and throwing strikes with the fastball has been significantly better than he was at times in the middle part of last season and the start of this season.” 

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