JUPITER, Fla. — A reliever whose brilliance in October “revolutionized” how teams now finish games is leaving the mound just as his latest, lasting impact on baseball is beginning.

Andrew Miller, a postseason MVP and 6-foot-7 lefty with a wicked slider who showed how the best reliever didn’t have to wait until the ninth to save a game, is retiring after a 16-year career, he told the Post-Dispatch. The 36-year-old pitcher spent the past three seasons with the Cardinals and the past three months as a measured, influential voice at the negotiating table representing the players’ union during bargaining that won greater earning power for the young players inheriting the game.

When needed, he always did know how to close.

“He changed the game,” said Adam Wainwright, the Cardinals’ veteran starter.

“He changed the game and he kind of took that relief role back to when it first started, guys who could do two, three innings – and he was the guy who did it in the postseason,” Wainwright continued. “I have an appreciation for what he did for the entire game of baseball. As many hours as that guy put in for the union over these past few years is kind of staggering. He may retire and that means this whole offseason he still spent 16 hours on the phone a day, for us, for who’s next – that means a lot.”

A two-time All-Star, Miller pitched for seven teams. He spent four years of his career with Boston, where faith from the front office allowed him to reinvent himself and relaunch as a reliever. He had a 36-save season for the New York Yankees in 2015, and the next fall, after a trade to Cleveland, had one of the most dominant playoff runs ever by a reliever. He set a postseason record with 30 strikeouts in the postseason, besting the previous record of 28. During the American League Championship Series he pitched 7 2/3 innings of relief in a five-game series, struck out 14 of the 25 batters he faced, and won the ALCS MVP.

Miller and Cincinnati’s Rob Dibble, in 1990, are the only relievers to win a postseason MVP award and not be their team’s primary closer.

“Playoff baseball is the greatest place to be and there is no better feeling in the world than having success on that stage,” Miller wrote in a text this week. “I feel very fortunate that my career worked out the way that it did. Of course there were tough stretches, injuries, and times of doubt. I also won’t deny that I can find myself in moments of wondering what if this or that had happened differently, could it have somehow been better? I’m usually pretty quick to be able to step back though and see how lucky I have been. The hard times were necessary for me to grow and to be able to appreciate the highs along the way. Ultimately, I was able to play for many great franchises, wear historic uniforms, and play in some amazing ballparks.

“I made some of the best friends I will ever have in life through the game,” he added. “I was able to work with the union and see the good it can do for players while learning so much about the game.”

Two years before he overwhelmed October and invited teams like the Cardinals to reimagine their bullpen use even during the regular season, Miller helped change how middle relievers were compensated.

A jackpot awaited top-shelf closers in free agency. Saves paid. But setup and targeted relievers didn’t come near the same level, even if they handled high-leverage assignments just as expertly. In December 2014, with one save on his baseball card, Miller signed a four-year, $36-million to wear pinstripes and pitch in the Bronx. It was the richest contract ever for a setup man. By the start of the 2016 season, six more of the top 10 contracts to non-closer relievers had been signed around and after Millers’.

As teams shook loose from the defining relief roles by the inning and the limits of saving closers for the ninth, metrics advanced with bullpen usage and so did salaries. Milwaukee lefty reliever Josh Hader was an All-Star receiving Cy Young award votes and before he got his 13th career save he received a $4.1-million salary in his first year of arbitration. And he lost that arbitration hearing. Hader’s teammate, Devin Williams, a Hazelwood East grad, won the Rookie of the Year award in 2020 as a reliever – who did not have a single save.

But he did have nine holds to go with that 0.33 ERA in 22 appearances.

What Miller did in Cleveland help make middle relievers rockstars.

“He certainly gave baseball teams something to dream about,” said his agent Mark Rodgers. “He was really a utility pitcher at the time – could do anything needed. … He’s a bit of a Renaissance Man. Curious. So many interests. Everyone who has been his teammate will tell you what a gentleman he is. But the person least impressed with Andrew Miller and his ability and talent has to be, without a doubt, Andrew Miller.”

Those early deals for non-closer relievers from 2014-2015 included two former Cardinals, Luke Gregerson and Pat Neshek, and inspired the Cardinals’ rush to outbid other teams for Brett Cecil. They signed the setup lefty to a four-year, $30.5-million contract and advertised how they wanted to find the next Andrew Miller. They had tried several times to acquire Miller, develop a Miller from within, or cast a free-agent reliever in that same role. Finally, before the 2019 season they just signed Miller.

“He kind of revolutionized all of it – your best pitcher doesn’t have to be your starter or your closer,” Cardinals pitching coach Mike Maddux said Thursday. “And he was the best pitcher on multiple staffs. What he did in the postseason to help his team was groundbreaking. I don’t think anybody really duplicated what he’s done – as far as throwing multiple innings in the hairy innings, whenever they are.

“He was like the secret weapon on any team he was on.”

In three seasons with the Cardinals – all of which ended in the playoffs, some of which were limited by injuries – Miller was 6-7 with a 4.34 ERA in 129 appearances and 103 2/3 innings. Miller, who purchased a retro redbirds logo tee shirt from the 1980s to wear in the clubhouse, struck out 126 batters as a Cardinal, of the 979 he had in his career.

Overall, Miller went 55-55 with 63 saves and a career 4.03 ERA.

In the postseason, Miller was 2-1 with a 0.93 ERA and 54 strikeouts in 38 2/3 innings. He was credited with one save and forever changing postseason pitching.

Initially drafted by Tampa Bay, the team nearest his boyhood home, Miller turned down a sizeable bonus to pitch at North Carolina. In June 2006, the Tigers drafted him sixth overall. In August 2006, he debuted – less than 50 days after the draft. He was with Detroit as they lost the 2006 World Series to the Cardinals. Before the 2008 season, he was a talent in the blockbuster trade that sent Miguel Cabrera and Dontrelle Willis from the Marlins to Detroit. Miller’s command and then his career started to drift as the Marlins kept him in the rotation.

Granted free agency shortly after a trade to Boston, Miller resigned with Boston and, with future general manager Ben Cherington as a champion, ignited his ability as a reliever.

“What I recall was a complete and total accountability as a young player, a high draft pick comes in and says whatever I have or haven’t done is on me,” said Cherington, now Pittsburgh’s general manager. “He had the conviction he was going to figure it out. Our hope was to somehow free him up to be the athletic Andrew Miller, the unique Andrew Miller. It wasn’t overnight. It wasn’t like he came to Boston – and boom! The career took off and really turbocharged after he left.

“His ability was part of changing the game, changing how people thought about their pitching staffs – not just bullpens,” Cherington added. “He became synonymous with the postseason, with how people saw what was possible with pitching use in the playoffs.”

He went from Boston to Baltimore to the record deal with the Yankees in part because he didn’t want to leave the Eastern Time Zone and force his family to stay up watching games.

First elected as a union rep while in Florida, that became a constant for Miller even as his role on the field changed. He was part of the Collective Bargaining Agreement negotiations in 2011, 2016, and then again this past year as the likelihood of a lockout gathered like a storm at the horizon. He became one of the leading, public voices for the union and, according to teammates, a steadying, studious presence for any of their questions. In conversations with the Post-Dispatch and other outlets he stressed the goals of the union were to improve the game on the field by eliminating the incentives teams have for tanking and reasons they have for keeping young players offer rosters. In a podcast interview with The Athletic’s Jayson Stark, Miller said, “Fans want to go out and see a competitive product, and that’s what we want to sell to them – the best version of baseball.”

On that podcast hosted by Stark and Doug Glanville, “Starkville,” Miller described his motivation as the stories he heard in the clubhouse about sacrifices made by players in the past. He said: “Gives you more than a little bit of a desire to carry that forward and pass it on to the next generation.”

As a member of the Major League Baseball Players’ Association’s executive board, Miller was present for the negotiations at Roger Dean Stadium, and along with Max Scherzer remained at the ballpark during the marathon talks that stretched toward 3 a.m. local time. Strides made during the Jupiter talks resulted in an agreement within 10 days and the swift start to a full 162-game season.

“Miller cares about his fellow players, and he got them back on the field, in a far superior position to where they were before,” wrote Hall of Fame baseball writer Peter Gammons for The Athletic.

Miller then took a vacation.

In a text message this week, Miller cautioned that he could “talk about the game forever.” He mentioned how the “big-league steakhouse dinner” should not be lost as a tradition, the joy he got from playing for several of the historic franchises, wearing Red Sox, the redbirds, and the pinstripes. Away from the field he’ll have a chance to ski, to skateboard, and to pursue all the interests Wainwright listed recently in the clubhouse, from wine to knowing the type of wood used to make Wainwright’s guitar.

“He’s a man who knows a lot about a lot of things,” Wainwright said.

Just not what his next role in baseball will be.

“The list of people who took me aside, put their arm around me, made me laugh when I needed to, or taught me something is endless,” Miller wrote in a text message. “It’s safe to say I would have been faced with the next chapter much earlier on if it weren’t for them. As someone who thought their career was practically over in 2010, to be able to experience everything I did along the way is incredible. You shouldn’t ever hear complaints from me. It was a heck of a run.”