In the spring of 2010, Johnny Cueto started becoming the Johnny Cueto that Giants fans have come to know.

“In 2010, I was just messing around throwing the ball,” Cueto said, “and my teammates were, like, ‘Man, you’re really nasty like that.’ I liked it, stayed with it and kept on inventing.”

In the first year of his six-year, $130 million contract, Cueto quickly has become a fan favorite, based in part on his 4-1 record and 2.65 ERA, but also because of his fun-loving demeanor and variety of windups that make every pitch a must-see.

You never know what you’ll witness next. Neither does the batter, which is the point. It could be a quick pitch. Or a Luis Tiant back-to-the-plate pitch. Or, as if he’s morphing into Stephen Curry after a game-winning shot from halfcourt, a shimmy pitch.

Or he could be crafty by simply employing his traditional windup, which he used on every pitch before 2010, when he might as well have been Matt Cain. Every delivery was the same, and his hair was just as short.

Coming a long way

Now Cueto, 30, has dreadlocks, an easy way about him on the mound (think: opposite of Jake Peavy) and an effective arsenal that makes him a nice fit in the Giants’ rotation, between Madison Bumgarner and Jeff Samardzija.

In an interview with The Chronicle, through interpreter Erwin Higueros of the Giants’ staff, Cueto said his many deliveries have helped accelerate his career by keeping hitters off balance and always guessing.

“I saw I had a lot of success and just kept doing it,” Cueto said, recalling his initial experiments with different deliveries. “Then after that, they started comparing me to Luis Tiant. I had never seen Luis Tiant pitch, but that’s who they compared me with.”

Tiant won 229 games through 19 seasons, mostly with the Indians and Red Sox and is known for his various windups, including a back-to-the-plate delivery in which a batter could see only the number on his jersey before Tiant uncoiled and threw a pitch.

With Cueto, a batter sees only No. 47 when the pitcher twists his body to face center field. He hesitates momentarily before thrusting toward the plate, trying to throw a batter’s timing off and make him unprepared for whatever pitch is coming.

Seeking better control

That was Cueto’s first windup alteration, coming after he began tinkering with a new delivery in a bullpen session during a mid-April series in Miami in 2010. His command was an issue as he spun off the mound toward third base after his release. His pitching coach with the Cincinnati Reds, Bryan Price, asked him to lift his left knee back toward the pitching rubber to create a better turn, improved balance and more deception.

Cueto cut down on his walks and eventually took it to an extreme by resembling Tiant on some pitches. Since then, he added a quick pitch (with an abbreviated windup) in 2014 and the shimmy pitch (which he calls “the rocking chair” because of how he swings back and forth) last season.

“You want to work every hitter differently,” Cueto said. “That’s just the way I do it.”

Considering Cueto’s repertoire — fastball, slider, changeup, cutter, curve — and the many variations of his windup, he could have a couple of dozen different looks.

All from the same arm slot, miraculously.

Until the last moment

So when does he decide which off-pace pitch he’ll use for which batter? Before the at-bat? Before the inning? During pregame meetings?

None of the above.

“I just decide at the moment,” Cueto said. “On the fly.”

No wonder no one knows which delivery he’ll use next. Even his manager is left to guess.

“I don’t know what he’s going to do, either, to be honest,” Bruce Bochy said. “I just know he’s going to mix it up out there. He’s come up with a couple that surprised me that added another second to his delivery.”

By the way, Bochy loves Cueto.

“He’s got great focus pitch to pitch,” Bochy said. “He’s fun to watch. He’s entertaining. How he thinks and his game plan, I enjoy watching him pitch.

“What’s incredible, with all his different deliveries, is how he maintains his command. He works all four quadrants as well as any pitcher I’ve seen.”

Opposition complaints

Not everyone appreciates Cueto’s creativity. Tigers manager Brad Ausmus objected during Cueto’s four-hit shutout of Detroit in August, less than three weeks after Cueto changed leagues and was dealt from the Reds to the Royals.

Ausmus complained to umpire Joe West that Cueto wasn’t stopping in his delivery and therefore it was illegal. “Really,” Ausmus said at the time, “the way the rule reads, you’re not supposed to even alter your motion. But they don’t enforce it.”

Rule 5.07 states a pitcher should be on the rubber with his pivot foot, facing the batter: “From this position any natural movement associated with his delivery of the ball to the batter commits him to the pitch without interruption or alteration.”

Is Cueto interrupting or altering his delivery? He wouldn’t be the only one doing so, and it’s a matter of interpretation.

Anyway, Commissioner Rob Manfred, in his quest to modernize the game, especially for the younger crowd, is OK with it if everyone’s not a cookie-cutter pitcher and a guy’s wacky windup becomes an online sensation. If it’s OK to shimmy in the NBA, why not in MLB?

A month before Ausmus popped off, Ian Desmond was a Cueto shimmy victim. As Cueto did his shoulder dance in mid-windup, the then-Nationals shortstop was so perplexed, he took his left hand off his bat, stood straight and gave up.

Called strike.

“That’s really Johnny’s creativity,” said Price, who oversaw Cueto for six seasons as Reds pitching coach and manager, in a phone interview. “He got more comfortable with his mechanics that day in Miami, but he became Johnny Cueto on his own. I’d love to be able to attach myself to the Tiant stuff and quick pitch, but that’s all Johnny.

“The beauty of Johnny is always trying to find an edge and not rest on his laurels.”

Happy not to face him

Giants hitters, after Cueto became their teammate, expressed how relieved they were to not have to face his tricky pitching anymore. And Buster Posey quickly learned how to catch baseball’s most artistic pitcher this side of Bartolo Colon, their work together Tuesday amounting to a 1-0 shutout of the Padres.

“We get along very well,” Cueto said. “He’s a very good catcher, and this is a long-term relationship.”

Speaking of which, the opt-out in Cueto’s contract allows him to ditch the Giants after two years, similar to how Zack Greinke bolted the Dodgers after last season and signed a record contract with the Diamondbacks.

Asked about sticking around after two seasons, Cueto said, “We’ll see what happens. I like the fans. I like to pitch here.”

His next start is scheduled for Monday in Cincinnati, where he broke into the majors in 2008, won 92 games and finished second in the 2014 Cy Young Award voting and fourth in 2012.

Cueto won’t deny he’ll fight emotions heading into the start. “Maybe a little,” he said. “I started my career there. It’s where I pitched and had some good years.”

John Shea is a San Francisco Chronicle staff writer. Email: jshea@sfchronicle.com Twitter: @JohnSheaHey