The legend of Amari Bailey sprouted in a preseason scrimmage with no one watching and nothing at stake besides the respect of his coaches and teammates.

A shot caromed off the rim. Bailey sprinted toward the basket from the corner. The freshman guard rose for a putback basket that swung a taut game permanently in UCLA’s favor.

“He was two feet above the rim and that put us up five and salted the game away,” said Bruins coach Mick Cronin, recalling the recent scrimmage against San Diego State. “We’re talking about a guy known for having all his talent with the ball, here’s a guy soaring up there to make a hustle play to win the game and that’s after playing major minutes. You would think he would be somewhat tired and he’s playing against 22-year-old and 23-year-old guys and he’s 18.”

Bailey isn’t up and coming. He’s here.

Maybe not for long.

“I don’t see him being here much longer than six more months,” junior guard Jaylen Clark said of his precocious teammate.

A McDonald’s All-American from Chatsworth Sierra Canyon High who was ranked as the nation’s third-best combo guard in his high school class, according to 247 Sports, Bailey might be exceeding early expectations based solely on his willingness to learn.

“If I tell him one thing, I don’t have to tell him again,” senior guard David Singleton said. “That’s the maturity level that he’s at. And it’s really rare to see a young guy have that.”

In his first two months on campus, the 6-foot-5 Bailey has busied himself mastering concepts such as learning the right angles to keep his man in front of him defensively and making the correct reads in the pick and roll.

“I’m the baby on the team, so I’m really just still getting acclimated,” said Bailey, who won’t turn 19 until February. “Coaches in practice tell the guys all the time, ‘He’s a freshman.’ So that’s helped me. And I’m really just trying to soak up as much as I can, being a sponge.”

Some of the most valuable lessons have come from the veterans. Senior small forward Jaime Jaquez Jr. has provided daily lessons in relentlessness. Senior point guard Tyger Campbell told Bailey that open spaces close up much quicker in college than in high school.

Bailey once played for the same Nashville-based club team, We All Can Go, that produced Campbell.

That is, until the coach cut Bailey as a fourth-grader.

“I definitely appreciate him to this day,” Bailey said of the coach, “because I definitely say that gave me more of a hunger knowing that you could be replaced at any given time.”

Bailey has already proved indispensable as a Bruin given that some qualities built into his demeanor can’t be taught.

“Amari’s got an inner toughness about him that’s really going to propel his career that I haven’t seen in a freshman,” Cronin said. “Like at San Diego State, when the game got tougher, he got tougher. When the game got more physical, he got more physical.”

Bailey also possesses a rare selflessness for someone so highly touted.

“Most McDonald’s All-Americans don’t defend and [instead] hunt shots cause people tell them that’s how they gotta play to get drafted,” Cronin said, “but he knows that that’s not basketball. He’s a basketball-savvy guy, very intelligent guy. He gets that you can have a great game and have eight points, eight assists, eight rebounds.”

Heading into UCLA’s exhibition game against Concordia on Wednesday night at Pauley Pavilion, Bailey said he’s just trying to make the most of his time as a Bruin, no matter how long — or short — that stay might be.

“This is a dream school of mine,” Bailey said. “So just being able to have some pride while I’m wearing the four letters, really. … I know what I did in high school doesn’t matter. I’m starting from square one again and really just learning the game.”