How did David Price dial up his velocity this postseason?

Barry Chin/Globe Staff

What the heck happened to David Price? How did the Red Sox lefthander, in the middle of the postseason, suddenly dial up velocity and develop a diving changeup that he hadn’t possessed at any previous point in the 2018 season?

To answer those questions, it makes sense to revisit some of what transpired during this year of adjustments for the veteran. In the middle of the season, Price and the Sox made the decision to have him lower his arm slot to create more angle on his pitches and less stress on his arm.

But over time, the drift became increasingly pronounced, particularly in the three appearances leading up to his ALCS Game 5 start. In those, Price had his three lowest average release points of the season — all between 5.7 and 5.72 feet off the ground when letting go of his two- and four-seam fastballs, below his season average of 5.85 feet.

With a lower arm slot, it became more difficult for him both to generate power on his pitches and attack hitters from the top to the bottom of the strike zone. (His 91.9 mile-per-hour average fastball velocity in Game 2 of the ALCS was a near-low for the season.)

Put another way, his stuff flattened.

But in Game 5, his average release point on fastballs was 5.91 feet — roughly 2½ inches higher than it had been in those prior three outings. The elevated release point was a product, however, rather than a cause of an improvement Price made to improve his posture and the aggressiveness of his tempo.

Whereas he’d worked to keep his shoulders more level in the middle of the year — something that improved his execution with his back-door cutter against righties — Price restored some of the tilt to his delivery, with more forward motion generating a velocity bump.

Price described the change as “just something that makes my delivery just flow a little bit better, kind of put my arm more on time for every throw. Just put me in a position to execute every pitch.”

The result? Price averaged 93.9 m.p.h. on his fastballs in Game 5 of the ALCS, his highest average velocity in any start of 2018 — and up a couple ticks from his 91.9 m.p.h. average velocity in Game 2 of the ALCS.

“I think he changed the way he pitched that game. His delivery was a little bit different,” said pitching coach Dana LeVangie. “He was working more back-to-front in his delivery. And I think the environment amped him up in a good way.”

The fastball became more explosive with more late life up in the zone. Meanwhile, Price threw his changeup harder than at any other time in the season, averaging 87.0 m.p.h. Between the greater velocity — which somewhat diminished the depth of the pitch — and the raised arm slot, Price was doing a better job of selling the changeup as a pitch that looked like a strike before diving late and hard out of the zone.

The Astros took Price’s changeup for the most part in the few instances where he threw it in Game 1, swinging at just three of nine (33 percent). But in Game 5, the alterations — plus the need for the Astros to speed up their bats to contend with the increased velocity of Price’s fastball — turned the changeup into a devastating swing-and-miss offering that played, in the words of Red Sox manager Alex Cora, more like a splitter in Game 5. Price threw 40 changeups; the Astros swung at 29 (73 percent), with 12 of those hacks resulting in swings and misses.

“More important [than the velocity bump] was the action to the changeup, which he was able to carry through the entire outing,” said LeVangie. “That made [the outing] that much more special.”

Price’s arsenal was as good as it had been in any outing of the year. As good as the stuff was, however, it was less impressive than the ability of a pitcher to make a subtle change to his mechanics to unlock something that he hadn’t featured in months.

Some pitchers require weeks to make even small changes to their delivery. But Price is a tinkerer, someone who in the past has been consciously willing to change his position on the mound or his arm slot between pitches. In this instance, he used an incredibly high-pressure bullpen session in the middle of Game 4 of the ALCS to position himself to help lead the Red Sox past the Astros and into the World Series, where he got the Game 2 start.

“His ability to make adjustments on the fly,” said LeVangie, “is what makes him really unique.”