De’Aaron Fox goes up for a dunk against UCLA on Friday night. (Andy Lyons/Getty Images)

MEMPHIS — It is not true what they say about Kentucky and four-year players, at least not entirely. John Calipari’s program really does retain some guys for the duration of a college career. Two of them are guard Dominique Hawkins and forward Derek Willis, a pair of Wildcats seniors who have, to put it lightly, seen some stuff.

Hawkins and Willis have counted as teammates, among several other current NBA players, Julius Randle, Karl-Anthony Towns, Tyler Ulis, Jamal Murray and Devin Booker, who on Friday night scored 70 points in an NBA game. They are a pair not easily impressed, a pair whose comparisons carry weight. And this is what they see in De’Aaron Fox, the freshman guard in the process of taking this NCAA tournament in his hands.

“He’s one of the more athletic kids I’ve played with — definitely the quickest I’ve played with, for sure,” Willis said. “His athleticism elevates his game so much.”

“He’s definitely the best point guard I’ve been around, athletic-wise,” Hawkins said. “It’s just insane that he’s improving. I’ve never seen a guy improve as much as he has during the season.”

The FedEx Forum court flooded with stars Friday night, and Magic Johnson snagged a first-row seat to watch next to Los Angeles Lakers General Manager Rob Pelinka. Lonzo Ball and Malik Monk entered the night on the marquee. It belonged, by the end of Kentucky’s 86-75 South Region semifinal victory over UCLA, to Fox.

Fox scored 39 points, an NCAA tournament freshman record, on only 20 shots. He battered UCLA with floaters, midrange jumpers and driving layups, the product of devastating pick-and-rolls. On defense, he helped end Ball’s career in unsightly fashion, holding Ball, with the help of teammates, to 10 points on 4-of-10 shooting, including 1-of-6 from three-point range. Afterward, Ball declared it, as expected, his final game.

The contrasting performances of Ball and Fox gave NBA evaluators something to mull over. Pelinka, newly installed as the Lakers GM, may be choosing one of the first players in the loaded, upcoming draft. He cannot comment on underclassmen, and he wouldn’t tip his hand, anyway. But the reason he traveled to Memphis was to see how top players perform against one another, and Fox thoroughly dominated Ball.

“You want to see the best players play in a huge game like this and see how they respond,” Pelinka said. “It’s very important. A big thing when you’re judging talent is how guys compete at the highest level.”

Fox might be both the fastest and most relentless player in college basketball. He slithered to the rim whenever he wanted. By the end, Ball had turned weary and Fox remained a current of electricity.

The Sweet 16 hosted Fox’s breakout and provided Ball only misery. The Wildcats hounded him with an array of players, wearing him down with Fox’s speed, Isaiah Briscoe’s muscle and Hawkins’s quickness. They knew Ball preferred passing to scoring, and they focused on leaping when he leapt, not to block his shot, but to fill passing lanes. Ball finished with eight assists, but he scored only two points in the second half. As he wore down, the Wildcats overwhelmed the Bruins.

“I noticed that he was throwing the ball to [Aaron] Holiday and then walking up the court,” Hawkins said. “I could sense that he was a little tired. We were pressuring him the whole game, to try to get him tired.”

“He started limping at the end of the game,” Fox said. “I don’t know what happened. With like five minutes left, we were running to our huddle. We saw them walking. We were like, ‘Look at them. They’re getting tired.’ ”

On offense, the Wildcats came with an equally punishing plan for Ball, also centered on Fox’s singular athleticism. Calipari declared they would run their offense, every possession, through Fox. Kentucky was vicious with its pick-and-roll.

“Lonzo Ball, it just wasn’t good for him,” Willis said. “He got kind of caught up when a big screened him.”

While Ball attempted to fight around screens, most of them set by freshman Bam Adebayo, UCLA’s big men, as instructed, drifted back to the hoop, wary of yielding a lob. They also refused to sag off Willis and Monk on the wings. The coverage dared Fox to beat them.

“I would probe, and no one would guard me,” Fox said. “I was like, ‘I have to make these floaters.’ And I was making them.”

He continued a late-season trend. In the regular season, Fox averaged 15.5 points, tailing off at the start of Kentucky’s SEC schedule. Calipari hammered on him to be more aggressive, and to absorb contact on drives to the hoop instead of flailing in hopes of drawing a foul. Fox, one of the nation’s best recruits, had never been coached so hard. He relied on the advice John Wall, a product of the Kentucky factory, gave him: “When Cal gets on you, don’t take it personally. He just wants the best for you.”

“Coach asks a lot out of the point guard position,” Willis said. “It’s tough to play here. It’s real stressful. If you can’t handle it, it’s not the place for you. You have to play fast, and when you’re as fast as Fox, they’re going to ask even more out of you.”

Fox has delivered when it’s mattered most. In Kentucky’s six postseason games, he has averaged 23 points. Friday’s performance reached a new level.  The pick-and-rolls provided a vivid warning to North Carolina, Kentucky’s opponent in Sunday’s regional final.

As Fox has emerged as more of a scoring threat, Kentucky has developed a frightening offensive identity. Kentucky is not only a defense capable of holding UCLA, the best offense in the country, to 15 points below its season average. It also forces defenses to guard shooters, a muscular, rim-running big man and, now, an electric point guard capable of taking over games.

“If we had to do it all over again, I don’t know if we’d change our game plan,” UCLA guard Bryce Alford said. “He was just phenomenal tonight.”

Fox’s only blemish came when he bricked a late free throw with a chance for a milestone. Monk, his fellow freshman, told him, “Man, you’re scared to get 40.” Fox just laughed. He had taken his place among Kentucky’s recent greats and taken over the NCAA tournament. He had nothing to worry about at all.