JUPITER, Fla. — Weeks before his first spring training hit, Brendan Donovan was already trying to turn that single into a double.

After weight training Friday at the Cardinals’ facility, Donovan spent an additional 30-plus minutes outside under a canopy, while watching clips and working on footwork with a coach.

There are extra bases out there to steal — and, of course, steals to steal, too — and Donovan wants to maximize his abilities. For all that’s made about his scrappiness and hair-flapping hustle, he thrives because of his meticulousness and attention to detail. He developed one of baseball’s best eyes for strike-zone awareness and hands that earned him a Gold Glove, all in his rookie season. Now, regarding his feet, he’s fine-tuning his footwork. He’s not the fastest runner. But, as we’ve seen with Paul Goldschmidt, any player can still develop into the smartest runner.

“If you can gain a step, not only can you cut the bases a little more efficiently, but I think that you can maybe steal a hit, here and there — or at least cause something to happen that can help your team win,” Donovan told The Post-Dispatch after his day at the office. “So that’s been a big emphasis this offseason.

“It’s the nitty-gritty details. Looking at the (jump), obviously. And then, for my cue, it’s just attacking the ground and attacking back, so you’re putting force down in the ground — and then backwards — so you can propel yourself forward. It’s just all technique. Sprinting is so fine-tuned.”

It’s cool to see “the before.” The ballplayer in the “lab,” as they say, working on tinkers and tweaks to best prepare himself for spring games. With a season already on his résumé, he’s resuming work as if he were a rookie. And that’s a cool trait.

“I think that’s what the best players do,” said Donovan, whose clubhouse locker was close to both Albert Pujols and Yadier Molina last season. “I had obviously the pleasure of seeing some of the greatest ever do it this past year. And then that’s what they do. That’s how they stay so consistent. That was a treat last year — I learned so much. I’m glad I was able to take that and then bring it down here and be around the complex, be around this staff — and just put it to work.”

Donovan sure is fascinating. In a game with so many clones, his prototype is rare. His slugging percentage (.373) was actually lower than his on-base percentage (.394). He had 70 strikeouts and 60 walks. And defensively, he arrived right on time — his first year was the first year Rawlings awarded a utility Gold Glove (makes one wonder how many Jose Oquendo would’ve won?). Per the Elias Sports Bureau, Donovan became the only player since 1900 to start at four different infield spots in his first four Major League Baseball starts. He would go on to play outfield stints in right and left — and even started 11 games as the designated hitter.

Hitting .281 overall with a 126 OPS+, Donovan earned the honors of being the top rookie in the National League … who didn’t play for Atlanta. Alas, Brendan finished third in the rookie of the year voting, behind the Braves’ Michael Harris II and Spencer Strider. Still quite impressive.

“When I think about him, my immediate thoughts gravitate to just, like — a baseball player. A baseball rat,” said John Mozeliak, the Cardinals president of baseball operations, during a quiet moment in Jupiter. “Loves to be around the game, plays hard, works hard. And saw tremendous results because of that. So I think the biggest thing for Brendan, as we think about 2023 is — what can he build upon? Is what we saw last year who he is? Or is there more there? I am an eternal optimist. I do always believe that we never should define ceilings and try to determine — ‘Oh, he’s met that.’

“So I look at 2023 for Brendan Donovan as — he’s going to find his way in our lineup. He reminds me of water running down the hill — it’s going to get there. That’s what he’s going to do. Whether that means he’s getting everyday at-bats at second base, or that means he’s getting everyday at-bats playing all over, time will tell. Some of that he controls, some of it he doesn’t. But ultimately we love him as a player. I think what he brings to the game is amazing.”

As a lefty hitter, one would assume Donovan will get some extra hits due to the shift ban. And his plate discipline earns him so many walks already. He’s got Matt Carpenter eyes. Donovan ranked in the 93rd percentile for walk percentage, per Baseball Savant. He just doesn’t swing as much as other players. And when he does, he makes contact at a higher rate than most other players.

“He’s never off balance,” said Tommy Edman, the Cardinals’ starting shortstop, who will play alongside the second baseman Donovan (when Donovan isn’t playing a secondary position). “He never really stepped out of control in his at-bats. I think that’s one of the big things you notice about the best hitters out there — they seem to be in control of their at-bats. No matter who’s pitching or how nasty a guy’s stuff is, they always seem comfortable in there. And that’s something that he does. And obviously, it helps him see pitches well and swing at the right pitches.”

But here in Jupiter, he’s yet to face any pitches — in games, anyway. The Cardinals’ spring training opener isn’t until Feb. 25. But Donovan is fastidiously working on getting faster, step by step, because that single he can make into a double could occur in February, July or, even, October.