Arizona guard Nick Johnson (13) slams home the alley-oop dunk during the first half of the University of Arizona vs. Oregon State men's college basketball game on Wednesday, March 5, 2014, at Gill Coliseum in Corvallis, Ore.

Mike Christy / Arizona Daily Star

ORLANDO, Fla. — If there were still any NBA-level doubts about former Arizona guard Nick Johnson’s ridiculous leaping ability, they likely ended midway through the third quarter of his first NBA Summer League game with the Houston Rockets on Saturday.

Johnson, already turning in a promising debut, drove to the basket from the left side, took off and pulled off a high-flying, left-handed dunk on a 6-foot-10 Pistons center that quickly went viral.

That play, as part of an 18-point game in a team-high 30 minutes, left a curiosity for just how much the second-round pick — taken with 42nd pick overall — can elevate himself this week.

“It was fun,” said Johnson, who went 7 for 14 from the field with a pair of three-pointers, five rebounds and three assists at Amway Center. “Coming in here, I was really excited. I get to showcase my talents and prove some people wrong.”

NBA second-round picks don’t have guaranteed contracts — disappoint, and you’re playing in the NBA Development League or overseas — so they’re often the hungriest, most motivated players in summer league, where everyone but the highest draft picks is trying to show they belong on an NBA roster.

“I don’t feel like there were that many people better than me in this draft,” said the 21-year-old, who was the Pac-12 Player of the Year as a junior at Arizona. “I’ve been proving people wrong my whole life, so it doesn’t stop now.”

Houston has found success in the second round before, including the team’s No. 3 scorer last season, forward Chandler Parsons. After just one game, a headline in Sunday’s Houston Chronicle said the Rockets may have found “more 2nd-round gold.”

Johnson will wear No. 3 with the Rockets — the same No. 3 his uncle Dennis wore with the Celtics in the final seven years of a Hall of Fame career, playing alongside Rockets coach Kevin McHale.

On Saturday, Johnson had familiar faces around him in Orlando — teammate Aaron Gordon, the draft’s No. 4 overall pick, is here with the host Magic, and the two have hung out in the players’ hotel. Former Arizona State guard Jahii Carson, who went undrafted after his sophomore year, is also on the Rockets team, and he had six points, four assists and two steals Saturday.

Johnson has another four games in Orlando to leave a strong first impression with his new team — on Monday afternoon, he’ll go up against Gordon and the Magic. His path to sticking on an NBA roster is a simple one: keep the drive of a second-round pick, while showing why that chip didn’t need to be on his shoulder in the first place.

“I just need to come in and work,” he said. “I believe they see that I can play defense, use my athleticism and I want to showcase that, showcase that I’m a complete player that can play the 1 (point guard) and the 2 (shooting guard). It’s just going out there and working.”