This one stemmed from a mechanical glitch that left the middle finger of Miller’s pitching hand throbbing after the right-hander, in his third start for an Arizona team that traded away its top prospect to acquire him in 2016, jammed his hand into the mound on the follow-through of a second-inning pitch in San Diego.

“I’ve never seen anybody hit his hand on the ground like that — ever — and it wasn’t like it was one time, it was multiple times,” said Mike Butcher, the Diamondbacks pitching coach from 2016 to 2019.

“I was like, ‘What the heck is going on here?’ It was almost like jamming your finger with a basketball, and you’re trying to throw a baseball. It definitely affected him.”

Miller has no idea how or why he smacked the front of the mound in Petco Park on that April night in 2016 — it had never happened in four minor league seasons and three big league seasons in St. Louis and Atlanta.

Shelby Miller jams his hand into the mound during a game with the Diamondbacks in April 2016.

But the freak injury seemed to trigger a cascade of calamities for a pitcher who went from an All-Star season in 2015 to a Class AAA demotion in 2016, Tommy John surgery in 2017, a premature comeback and disastrous 2018, a shoddy 2019, a dormant 2020 and 2021 and 2022 seasons spent mostly in the minor leagues, where he transitioned to the bullpen.

Almost seven years later, Miller, 32, will attempt to revive his career with an organization known for turning scrap-heap acquisitions into highly productive big leaguers, the burly 6-foot-3, 225-pounder signing a one-year, $1.5-million major league deal with the Dodgers on Dec. 2.

“It’s one of those things where you kind of have to ride the wave, man,” Miller said by phone from his home in Phoenix. “I’ve had a ton of success in the big leagues, I’ve struggled a bit these past few years, and it was an eye-opening experience playing in the minor leagues.

“It kind of brings you back to loving baseball again and the grind, of being gritty and trying to get back to the big leagues, and I’ve done that. So I’m pumped to be able to say I stuck around and didn’t give up.”

Miller was beginning to wonder if he would get another big league shot. Released by four organizations from 2019 to 2021, Miller spent 5½ months of 2022 with the Class AAA teams of the New York Yankees and San Francisco Giants, compiling a 2.87 ERA with 12 saves, 69 strikeouts and 21 walks in 53 1/3 innings of 43 games.

But it wasn’t until Sept. 22 that Miller was finally called up by the Giants. He threw 5 2/3 scoreless innings in three games before being roughed up for five runs in 1 1/3 innings of his fourth and final game.

“I was dominating in the minor leagues and was getting to that point where I was like, ‘There’s nothing more I can do,’ ” Miller said. “I told my wife [Erika] that if I don’t get called up, I’m never going to. But I never quit, I kept working hard, I got that opportunity and took off with it.”

The Dodgers took note of Miller’s still-lively 94-mph fastball, sweeping slider and high whiff rates and identified him as a reliever on the rise, one who could help ease the loss of injured setup man Blake Treinen and supplement a bullpen led by Daniel Hudson, Evan Phillips, Alex Vesia and Brusdar Graterol.

Shelby Miller delivers during a game between the Pittsburgh Pirates and the Philadelphia Phillies in September 2021.

(Matt Slocum / Associated Press)

“He had a lot of success in triple A and has fully transitioned to being a reliever,” Dodgers general manager Brandon Gomes said. “It’s an interesting throw — a fastball with a kind of low-slot, rise-and-run, and the slider plays off that. We feel like he’ll have a high strikeout rate with an average walk rate.”

Miller has begun throwing bullpen sessions with assistant pitching coach Connor McGuiness at the team’s spring training complex in Phoenix and is in constant phone contact with pitching coach Mark Prior.

He’s working on a split-fingered changeup, an 89-mph pitch with good diving action that he thinks “will be really good,” and an upper-80s cut-fastball.

“We’re seeing how we can tunnel pitches better off the heater and trying to perfect my craft a bit,” Miller said. “These guys are so knowledgeable. Connor and Mark are amazing dudes who know a lot about pitching, how to get guys out, how to get swings and misses, and how we can do this every day.”

Miller had a five-pitch repertoire as a starter and established himself as one of the game’s better young pitchers in 2013, earning a spot in the Cardinals rotation as a 22-year-old and finishing third in National League rookie-of-the-year voting.

He went 31-35 with a 3.27 ERA in 95 starts in three seasons (2013 to 2015) with St. Louis and Atlanta and made his first All-Star team in 2015, but his career nose-dived after he was traded from the Braves to the Diamondbacks at the winter meetings in 2015.

Arizona had pried Zack Greinke, the 2015 NL Cy Young runner-up, away from the Dodgers with a six-year, $206.5-million deal and viewed Miller as the final piece to a championship-caliber rotation that included Patrick Corbin and Robbie Ray.

So the Diamondbacks sent shortstop prospect Dansby Swanson, the first overall pick in the 2015 draft, and two other players to Atlanta for Miller, a trade that was widely panned when it was announced and looked worse a few years later.

While Swanson thrived in Atlanta, Miller went 5-18 with a 6.35 ERA in 29 games for Arizona, a three-year stretch Miller described as “a roller-coaster ride.” In reality, it was all downhill, starting with the game in which he jammed his fingers into the mound, an injury that forced him out of that game after two innings.

Atlanta Braves starting pitcher Shelby Miller delivers against the New York Mets in September 2015.

(John Bazemore / Associated Press)

“I’ve always had a really long follow-through, but that was definitely a weird moment, and we really couldn’t pinpoint a reason why it happened,” Miller said. “After that, I got into a bit of a rut.”

Miller went 2-9 with a 7.14 ERA in 14 starts in 2016 before being demoted to Class AAA in early July. He returned in late August and finished with a 3-12 record and 6.15 ERA in 20 starts.

“His fastball still had pretty good velocity, but he wasn’t able to spin the ball, and it affected his command,” Butcher said of the finger injury. “I don’t want to make excuses for him, but for me, it affected his game, big-time.”

What seemed like a minor physical issue morphed into a bigger mental one.

“I was coming off an All-Star season and had never really struggled like I was, and I was just scratching my head, wondering what the heck was going on,” Miller said. “I started trying to fix everything and got into my own head. It was kind of a downhill, spiral effect.”

Miller’s struggles put a drag on a team that was expected to contend for a division title but finished fourth with a 69-93 record, after which manager Chip Hale and GM Dave Stewart were fired.

“I think he put a lot of pressure on himself to be ‘the guy,’ to perform at a higher level, because he knew we traded a lot to get him,” Butcher said. “He was trying to be perfect in an imperfect game.”

Miller tore his elbow ligament in his fourth start of 2017 and had Tommy John surgery in May. He returned in late June 2018, 13 months after surgery — “I kind of rushed back and wasn’t ready,” he said — and went 0-4 with a 10.69 ERA in five games. He was let go after the season.

“Those Arizona years,” Miller said, “we’re a little cuckoo.”

So were the next four years, in which Miller made only 36 big league appearances and opted out of the 2020 season because of the coronavirus. But he showed enough in 2022 to warrant a guaranteed big league contract from the Dodgers.

“My family and my friends kept me going, everyone telling me, ‘You still got it,’ just believing in me, making me not want to stop playing,” Miller said. “I have a lot left in the tank. I think I’m gonna have a big year in 2023. I’m excited for it.”