Kemba Walker is blown away by De'Aaron Fox's playing speed and control and sees the PG as a future NBA All-Star. (1:02)

LOS ANGELES -- The first thing Kemba Walker and Marcus Smart noticed with De'Aaron Fox was the Sacramento Kings point guard's Mach speed.

"He makes fast people look not fast," Smart said, practically shaking his head.

Fox has some news for his impressed teammates.

"I think I probably have gotten faster," said the point guard who's entering his third NBA season.

This might be music to Gregg Popovich's ears as USA Basketball prepares for next month's FIBA World Cup. With Kyle Lowry recently withdrawing from Team USA due to his surgically repaired thumb, Fox has a prime opportunity in front of him. Initially, Fox was on the select team but has since been promoted to the senior squad with a need at point guard.

Fox is doing his best to impress thus far. After seeing Fox's speed up close, Walker said he thinks Fox is the fastest player in the NBA with a basketball in his hands.

"Oh, my goodness," Walker said. "He is super fast. His quickness is crazy. His end-to-end speed is ridiculous. ... That's scary if he's gotten faster. The thing about him is he's fast but really under control."

During USA Basketball's 97-78 exhibition win over the select team last Friday, Fox scored 12 points and had 3 rebounds, 3 assists, 3 steals and 2 blocks in 15 minutes. He also made 6-of-9 shots, but Fox said Popovich got on him for passing up shots.

Walker said it's only a matter of time before Fox is an All-Star. But the Boston Celtics point guard believes Fox can take his game up another level if he adds a consistent perimeter shot. Last season, Fox improved his field goal shooting percentage to 45.8% and 37.1% from behind the 3-point arc after shooting 41.2% overall and 30.7% from 3-point range.

"What impressed me the most is probably his shooting," Walker said. "He has really been knocking it down. That is what is going to take him to that next level. Like for myself entering the league, the next step for me was my jump shot. That is what helped me get to the next level."

"Whenever he consistently gets that, it will be over," Walker said. "It will be over. No question."

Guard De'Aaron Fox has opened some eyes with his speed as Team USA prepares for next month’s FIBA World Cup. Initially, Fox was on the Select Team but has since been promoted to the senior squad with a need at point guard. Gary A. Vasquez-USA TODAY Sports

On Wednesday, Fox, Kyle Kuzma, Joe Harris, Myles Turner and Jaylen Brown were walking through plays on another court when Team USA lost a scrimmage, 36-17, to a select team led by Jeff Van Gundy that was made up largely of some young pros, including Justin Anderson and G League players.

This men's national team has lost practice scrimmages before and still looked good in last week's exhibition. Still, there's plenty to work on before the World Cup, including developing chemistry. With several of America's star players withdrawing to prepare for the upcoming NBA season with the timing of September's World Cup, Popovich has a young roster with a group of players who don't have much international experience.

Like many of the players trying out for the final roster, Fox hopes that this USA Basketball experience will lead toward a breakout NBA season with the up-and-coming Kings.

Fox says he already has picked up leadership tips from Lowry and Smart and has tried to hold new teammates accountable even if he isn't comfortable playing with them yet.

"I think it is a big opportunity just being able to be here," Fox said. "I think I have gotten better as a player, as a leader, understanding of the game entirely. And if I am able to be on this team and travel with this team, it's a big success."

"Jerry [Colangelo] even talked about the 2010 team, all those guys being around 21, 22, 23 years old," Fox said of what USA Basketball's managing director told him. "He kind of sees the same thing and using it as a springboard into the season."