Zion Williamson knows he has a lot to learn starting when he makes his NBA Summer League debut.That said, he's already picked up a few things.The No. 1 overall pick in this year's draft by the New Orleans Pelicans is in Las Vegas, where his first game on Friday is officially sold out and, predictably, a hot ticket on the resale markets. After practicing Tuesday, Williamson said he's noticing that some of the rules of defense in the pro game seem a bit more offense-friendly than the zones he often saw in college."I do like the spacing a lot more," Williamson said, in a video posted to the Pelicans' web site. "You can't really just stand in the paint, so it gives me a lot of room to operate. Defense is just a little different as well."New Orleans plays New York on Friday night in the opener for both teams in Las Vegas. The four-team leagues in Salt Lake City and Sacramento continued Tuesday, with both set to wrap up Wednesday before all 30 NBA teams — plus the Chinese and Croatian national teams — arrive in Vegas in what has become an annual convention of coaches, players, scouts and executives.And, especially on Friday, plenty of eyes will be on Williamson."He's so explosive," Pelicans summer league coach Fred Vinson said. "You get him inside, especially create some mismatches, he can definitely be tough to handle."Pelicans guard Frank Jackson was in summer league last year as well, and said he's already noticing a much different feel this year.The Williamson effect is just part of that."Every guy we have here wants to win and wants to get better every single day," Jackson said. "I think there's an energy in New Orleans now that everyone can feel and we're ready to get it rocking."TUESDAY'S GAMESSALT LAKE CITY SUMMER LEAGUESPURS 99, GRIZZLIES 84Keldon Johnson scored 29 points and made a 55-footer to end the third quarter, and San Antonio (2-0) didn't have much trouble with Memphis.Johnson was 10 for 17 from the floor."I've definitely got some things I can improve on," Johnson said.Ben Moore scored 16 points, Jeff Ledbetter had 15 and Thomas Robinson added 14 for the Spurs, who led by 22 points in the second quarter and kept control the rest of the way.The Spurs gave several players the night off, including Lonnie Walker IV.Dusty Hannahs scored 20 points for Memphis (1-1). Paris Lee had 13 for the Grizzlies, and Ben Lawson and Tyler Harvey each added 10.___More AP NBA: https://apnews.com/NBA and https://twitter.com/AP_Sports