Two-and-a-half seasons into his NBA career, surprise one-and-done Devin Booker has transformed into a borderline All-Star and arguably the third-best player to come out of the 2015 draft. During the pre-draft process scouts questioned if Booker -- who would go on to become the No. 13 pick -- could become more than a shooter in the NBA. His size, stroke, feel for the game and footwork were impressive, but if he was going to remain the quick-action shot-maker teams saw at Kentucky, would he tick enough of the other boxes on both ends to warrant a lottery selection?

"When we got to Kentucky, everyone said they're going to sacrifice," Booker said after a December game. "We had such a talented team. You see Karl-Anthony Towns shooting 3s now, [John Calipari] wouldn't let him do that. So we all had a role on that team that we all followed. I think once I got in those draft workouts teams realized, 'Oh, he can put the ball on the floor a little bit.'"

At age 21, Booker has developed into much more than a 3-point threat. He's the Phoenix Suns' future and present -- an evolving three-level scorer, smooth pick-and-roll player and a budding facilitator.

Through 40 games this season Booker is one of only 10 players averaging at least 25 points, five rebounds and five assists per 40 minutes. The others? Stephen Curry, LeBron James, Kevin Durant, Giannis Antetokounmpo, James Harden, Damian Lillard, DeMarcus Cousins, Blake Griffin and Russell Westbrook.

Sure, some of that is a product of Booker carrying a heavy load for a bad Suns team (his true shooting percentage ranks eighth in that group). But of those 10, only Giannis and Booker are younger than 27.

Here's how he surged passed expectations for a late lottery pick, and what we can learn for future drafts.

How he's improved

While the fact Booker has greatly outplayed his draft slot is due partially to teams misevaluating certain aspects of his game, the majority of it is a product of his continued development. He has added new elements to his game every season, and it's his growth as a ball-screen and isolation player that has really taken him to new heights.

In 38 college games and 248 half-court possessions, Booker used only eight pick-and-rolls (2.3 percent of his offense) and four isolations (1.2 percent of his offense), according to Synergy Sports. He made only 12 shots around the rim (floaters and finishes), which is fewer than one every three games.

At the NBA level, though, Booker is Phoenix's workhorse. He has the eighth-highest usage percentage in the NBA, ahead of Curry, LeBron, Lillard and DeMar DeRozan. According to Second Spectrum data, Booker receives on average 21.9 picks per game. Although he hasn't been overly efficient, he has developed into a scoring threat out of ball screens and would likely be even more successful with additional talent around him.

The pick-and-roll has made up 26.7 percent of his offense for the second consecutive season, more than 10 times his rate at Kentucky. Not only has he been saddled with much more responsibility since the moment he landed in Phoenix, but he's proven capable of handling it. It's the combination of added volume and individual improvement that has allowed him to look like a future All-Star and one of the top young offensive guards in the NBA. But what specifically about Booker's game has allowed him to turn into more of an on-ball threat than scouts expected?

1. Expanded pull-up game

Booker's ball-screen and isolation success starts with his ability to hurt defenses with his pull-up. Although he didn't get many opportunities to show himself as a shot creator at Kentucky, in retrospect it should have been a bit easier to see this coming when you consider his size, footwork, touch and feel. Given the spacing of the NBA game, players with his tools usually develop into threats, even if they aren't full of burst or wiggle.

His crisp footwork, especially, could have been indicators of him turning into a more dynamic pick-and-roll pull-up shooter. Looking back, the eye test supports what we know now:

play 0:06 Booker made jumper Booker is assisted by Tyler Ulis.

His on-the-move shooting potential also could be seen in his tremendous elevation, balance and touch when sprinting off screens. He had an excellent base exploding into his jumper and did a great job getting square in the air and shooting near the peak of jump.

But there are plenty of NBA snipers who do a great job on the move without becoming prolific pick-and-roll shooters (Kyle Korver, JJ Redick, Klay Thompson). Booker has become more comfortable with the ball, operating at different speeds and keeping defenses honest with his pull-up game. While partially a function of his role, Booker barely put the ball down more than once or twice on a possession at Kentucky. His now-crisp handle really stands out in his NBA film, and it's deep pull-ups like this that set the table for the rest of his attack.

Dillon Brooks does a great job getting into Booker's body early, but all he needs is a small window to dribble into his pull-up from 30 feet.

Whether in ball-screens or isolation situations, range like this makes Booker a really tough cover in the half court, as he's knocking down a career-best 3.1 3-pointers per 40 minutes and at a 38.5 percent clip.

Booker isn't a guard teams can use drop pick-and-roll coverage against, as he's too much of a threat to rise up either from 3 or in midrange spots. Even when big men meet him at the line, he's more than comfortable knocking down tough pull-ups with range. Through 40 games Booker is scoring 0.934 points per possession on pull-ups, according to Synergy Sports, which ranks in the 70th percentile, an increase from his first two seasons.

Even when teams do get into his body and get him off the 3-point line, he does a great job of bouncing out with step backs or using his size, handle and pace to get to midrange spots.

Opposing coaching staffs usually try to show him different looks. They'll be physical with him at the point of attack, blitz him with aggressive traps to get the ball out of his hands or switch onto him and force him into a contested jumper.

While playing the law of averages is a sound strategy, Booker is still an extremely skilled isolation player, which is a major area of growth since his college days. After using only four total isolation possessions in 38 games at Kentucky, he averages just more than three per game at the NBA level, according to Synergy Sports. While a lot of teams opt to switch against him, his ability to elevate into his jumper makes him tough to contain.

He also does a great job of using slight nudges or stop-on-a-dime, behind-the-back dribbles inside the arc to create just enough space to rise and fire. In general, he has added a handful of combo moves to his once-basic handle, and that has unlocked his pull-up game accordingly.

While living off of contested pull-up 2-pointers isn't exactly the new wave of modern basketball, Booker is extremely gifted at doing exactly that both from the post and the perimeter. He's at his best against smaller 2s like Gary Harris and Avery Bradley, as he uses his elite footwork, handle and deception to get to his jumper at will.

play 0:15 Ulis made 3 Booker assists Ulis for the shot.

Although Phoenix isn't loaded with talent -- and Booker can be a bit trigger-happy -- he's doing a better job of blending scoring and playmaking while using the framework of his pull-up to set up the rest of his game.

2. Pace and getting to the rim

At Kentucky, Booker more or less played at one speed. Almost every time he put the ball on the deck it was to get to a midrange pull-up, which became predictable for opposing defenses.

It's a big reason why scouts weren't convinced he'd become more than a versatile shooter at the NBA level, as 89 percent of his total shots in the half court were jumpers and he attempted only 3.1 free throws per 40 minutes. His game appeared to be trending more toward Thompson than Harden, without the defense of Golden State's two-way star.

He was much more shooter than shot creator at the college level. Even when he had a lane to the rim he opted to hard plant and rise up in midrange spots.

While he still prefers pull-ups, Booker is doing a much better job of slowing the game down and reading the defense, getting into the paint for floaters, finishes or fouls. Only 65.6 percent of his shots are jumpers this season, and he's playing with pace while toying with big man and weakside defenders in pick-and-roll.

He needs to improve as an at-rim finisher, which was a real concern at the collegiate level as well. He's not a freak leaper and his so-so wingspan and average frame limit him a bit in traffic. Still, Booker never showed the live dribble game he has put on display now, and he's using it effectively.

We've seen how the threat of a jumper combined with NBA spacing usually eases concerns about lacking burst with the ball. Although still not full of wiggle and Kyrie Irving's chop-you-up sizzle, he has greatly improved his ability to get into the lane as the primary ball-handler. His efficiency can improve, but Booker is now making more than three at-rim shots plus floaters per game. His free-throw attempts per 40 minutes have more than doubled since college (now up to 7.4).

"Once you get known as a shooter like I did when I was really young, you gotta work on something else," Booker said. "People were closing out hard, I'd get by them, used to just one-two dribble pull-up. But now, obviously, the NBA game's a pick-and-roll game and I knew I had to work on that. I was working on it before college, in college, and now I'm getting a chance to display it."

Now he's freezing big men and guards alike:

play 0:07 Booker made jumper Booker gets the assist from Dakari Johnson.

Heralded defenders like Kentavious Caldwell-Pope have to respect Booker's triple-threat game as well. He does a great job of using hard jab steps and rip-throughs to get to his pull-up, which in turn opens up drives: