Nationals shortstop Trea Turner should thrive as Washington’s full-time leadoff hitter this season if given that opportunity. (Jeff Roberson/Associated Press)

Sitting by his locker, Trea Turner is slowly, meticulously wrapping the handle of his bat with sticky tape. “And doing a lousy job of it,” he mutters. What’s it for? “Supposed to be better than pine tar,” he says. So the tape is getting its chance.

That’s the nature of spring training — constant fiddling and experimenting, looking for any tiny edge in a new season. But Turner, even in this world, is significantly different. Not much about his game pleases him.

Which is curious because modern analytics (FanGraphs’ measurement of Wins Above Replacement) rated him one of the top 40 players in MLB last year, and the third best on the Washington Nationals after Anthony Rendon and Max Scherzer. Turner played all 162 games, scored 103 runs, led the NL in stolen bases (43), tied for the MLB lead in bunt hits (eight) and was a fine “plus” defender at shortstop.

“I was frustrated by myself last year. I could have done so many more things,” Turner says. “I’d think, ‘Why did I do that?’ or ‘That was dumb.’ I slid past the bag by an inch one time, got tagged out. ‘Come on.’

“I expect more from myself. And there’s more there. Am I going to hit [.342] like my rookie year? Obviously, no. But how much better is ‘better?’ Is it hit .290?” he says, pausing to think before each number. “Is it 20 home runs . . . 50 steals?”

Turner shakes his head — no, that’s not enough. He ups the ante: “With my speed and my hard-hit-ball percentage, there’s no reason I shouldn’t hit .300.”

What Turner doesn’t know is that only one shortstop in MLB history has ever had a .290-20-50 season — Hanley Ramirez — and he only did it one time, in 2007 when he was young, healthy and, most assumed, headed toward the Hall of Fame.

Now, Turner imagines those numbers as a norm. And he is probably right. His average the past three years is .291. He hit 19 homers in 2018. Manager Dave Martinez has, from the first day of spring training, volunteered that one of his goals for maintaining the Nats’ offense, especially without Bryce Harper, is to have Turner lead off as a rule and let him run wild — 75 stolen base attempts or more.

“I was looking at numbers [during the winter],” Martinez says. “Rickey Henderson — over 100 attempts. Tim Raines — over 90. Trea has 25-homer potential [someday] and 70 steals, too.”

Hearing about this, Turner gets a playful smile and says, “Seventy-five [attempts] is quite a bit,” perhaps imagining how much that would make his lean body ache.

If anybody doubts that Turner should be the Nats’ leadoff man, please stop it. In 63 games leading off last year, Turner was 22 for 23 on steals — a 57-steal pace for a full season. In his career, in 220 games leading off, he is 100 for 115 on steals (87 percent), a dazzling 74-steal pace for 162 games. Yet in 111 games when hitting in any other lineup spot, Turner is only 24 for 34 on steals, a 35-steal pace.

At 25, Turner is in his thievery prime. Most base stealers are of minimal statistical value. But at Turner’s efficiency level, you have a weapon. Use it.

On Saturday night here, the Nats played what will probably be their Opening Day lineup for the first time. Its main structural weakness is that four Nats either consider themselves leadoff men or have had the large majority of their career at-bats in that role — Turner, Adam Eaton, Brian Dozier (despite his reputation as a slugger) and Victor Robles, rated the No. 4 prospect in baseball, who has looked confident, hitting .360 with a .452 on-base percentage and three steals. The Nats also only have two regular left-handed hitters: Eaton and Juan Soto.

Batting Turner first and emphasizing a top-of-the-order speed game addresses all of these issues, at least to a degree. Eaton, a gifted bat-handler, hit-and-run man and bunter, is a fine No. 2 hitter who can use patience to give Turner chances to steal.

Although Eaton, who has a remarkable .394 on-base percentage in two years with the Nats, may steal a dozen bases, that’s not enough to distract the Nos. 3 and 4 hitters, Rendon and Soto. In fact, Rendon runs well enough that he and Soto may use the hit-and-run more this season.

With Ryan Zimmerman hitting fifth, this lineup begins right-left-right-left-right so that the Nats hide their excessive right-handedness until they get to the rest of the order, with Dozier batting sixth in front of a catcher (Kurt Suzuki or Yan Gomes) and a center fielder (Robles or Michael A. Taylor) at No. 8.

If the Nats prosper at speedy “small ball,” Martinez may bat Robles ninth at times so that he and Turner, two of the fastest men in the game, can try to turn the bases into a flywheel.

The biggest issue for Turner this season is how to exterminate his .271 average from 2018. Such a league-average standard is almost an insult for a man who blazed his way to 25 infield hits, plus those eight bunt hits. And he knows it.

“I felt like I hit the ball hard last season, but a lot of them were right at people,” Turner says.

Such bad luck, if you normalize Turner’s season for his career-long batting average on balls in play, probably cost him about 10 hits and denied him a .286 average. But Turner, with lightning hands on inside fastballs, quick-twitch hand-eye coordination and his wiry power, should probably be better than that.

Ever since Turner missed almost half of the 2017 season with a broken wrist from a fastball that tailed inside, he has seemed excessively conscious of that pitch. He never looked as comfortable at the plate in 2018, though he has steadily increased his walk percentage from 4.3 to 6.7 to 9.3 while keeping his strikeouts the same.

“I’m not scared,” Turner says. “But looking back, I could have created some bad habits. To me, it seems mechanical, not mental.”

This offseason, Turner took a long break from hitting to clear his mind and also, perhaps, loosen the grip of his mechanical habits since mid-2017. Piece by piece, he reassembled his swing mechanics, in particular cutting down his high leg kick so that he can wait longer to recognize pitches.

Turner’s quest has always been to become a high-quality hard-contact hitter, not a speedster who sprays the ball, beats out chops or bunts. “I don’t want to lead the league in infield hits because, at some point in my career, I can’t get away with it anymore,” Turner says. “I have to keep improving.”

Piece by piece, Turner has shown all the improving parts of his game. Except for that one wrist injury, he has been extremely durable since he was in the minor leagues. He has proved he can learn to take walks. His arm, once doubted, is now considered strong, and he has mastered his own way of making some tough defensive plays, including a trademark running jump throw.

But Turner hasn’t yet had a full year when he put all the pieces together. He hit with incredibly good luck (.388 batting average on balls in play) in 2016 but only arrived in the majors for a half-season. Injury sliced up 2017. Will this be the year when he hits with normal luck, fixes his mechanical glitch from 2018, continues to stay healthy and is finally allowed — and encouraged — to show whether he is a 50- or 60-base stealer?

In spring training, the answer, of course, is always, “Yes.”

In a matter of weeks, we’ll start to find out the results. No matter what he does, Trea Turner is unlikely to be anywhere close to satisfied. He’ll grump. He’ll tweak. But many others may be very pleased indeed.