– Mitch Garver had to apologize to his biggest fans, people so invested in his success that they invested their own money in a Garver jersey, too.

“One guy tweeted at me — ‘Hey, I bought your jersey and you switched numbers? What am I supposed to do?’ ” Garver said. “I felt a little bad about it.”

That’s what happens when a six-time All-Star who wears the same number arrives, though. Nelson Cruz owns 360 career home runs, and, Garver quickly realized, dibs on No. 23. Garver switched to No. 18, his fourth number in four training camps with the Twins, out of respect for his new 38-year-old teammate.

“Here you go, buddy, whatever it takes to hit 40 homers,” Garver said with a laugh. “I’m just really happy he’s here.”

Garver hopes the number switch is temporary, since he wore 23 as a tribute to his grandfather, a former professional fast-pitch softball pitcher; he would like to reclaim it when Cruz’s time with the Twins concludes. Garver is making another change this season, too — one that he hopes is permanent.

“I had some good receiving years in [Class] A ball, but ever since Double-A and Triple-A, I don’t think I was progressing as much [defensively] as I needed to. The bat was there; the glove, maybe not,” Garver said. “Honestly, I realized it was something I needed to address.”

A decade or two ago, Garver figures, his defense might not have been an issue, particularly considering his relative success with the bat — a .749 OPS as a rookie, roughly average among big-league catchers, after taking over as the everyday catcher when Jason Castro underwent season-ending knee surgery in May. But the statistical revolution wrought by adding StatCast tracking cameras to every ballpark has allowed teams to quantify exactly the effect that a catcher has on a game.

“Everything is measured now. Everything. And that includes how you receive pitches, how you steal strikes, how you move around,” Garver said. “It’s actual data — [analysts] can read the numbers and say, ‘He’s good at this, he’s not good at this part.’ ”

The numbers quantified a few too many flaws for Garver’s comfort. Analytics website Fangraphs estimated that Garver ranked 29th in defensive runs saved, among the 30 major league catchers with more than 600 innings behind the plate last year. And StatCorner’s count of “stolen strikes,” or pitches out of the zone that were called strikes, showed that Garver succeeded in successful framing about half as often as Castro, and placed him 40th among catchers who received at least 6,000 pitches in 2018.

The Twins showed him data that revealed his biggest weakness was in receiving low pitches, failing to get borderline pitches called in his pitchers’ favor. Veteran Bobby Wilson, called up when Castro was injured, was markedly better, which is why the “starter” was in the lineup 75 times and the “backup” started 45.

“Mitch is a young guy who is still learning and absorbing, and it’s up to us to provide the means to do so,” said Derek Falvey, the Twins chief baseball officer, who chose not to trade for another catcher when Castro went down. “That process doesn’t end [once you reach] the major leagues, and Mitch is an example of that. We have confidence in him.”

Having made an Opening Day roster for the first time last spring, Garver is eager to do whatever it takes to stay here. He hopes to split playing time in 2019 with Castro, who is healthy again, but doesn’t want there to be a dropoff defensively when he is in the game.

“The game is changing. I know I need to improve my receiving. I need to dominate the bottom of the zone, that’s what the best catchers are doing,” Garver said. “I’m trying to look ahead. I told myself I need to improve or else my chances might be closing. The door might be closing.”

In order to wedge it open, Garver approached General Manager Thad Levine about altering his offseason workout routine. Let’s add some intensive training behind the plate, Garver suggested, to the usual winter habit of weight training and batting cages. Levine reacted by setting up a couple of four-day workshops with the team’s catching specialists. Minor league coordinator Tanner Swanson flew to Garver’s Albuquerque, N.M., home in December to offer a clinic in receiving techniques, and shortly after New Year’s Day, Garver traveled to Fort Myers to meet and work with Bill Evers, the new catching coach on Rocco Baldelli’s staff.

The first thing the coaches did was convince Garver that he has the physical ability to be a good defensive catcher. The problem is technique, not talent.

“Absolutely it’s something you can learn. We made some changes, and you learn how and you get comfortable with it until you don’t think about it, you just do it naturally,” Garver said. “I’m excited to get into the bullpen and really show them where I’m at now. I don’t want to give away all my secrets, but I think we’ll see a change in my receiving this year.”