Lakers fans are having a ball as hope returns to L.A.

Mark Appelbaum sat courtside for most of the afternoon on Saturday at the Thomas & Mack Center wearing a maroon Lower Merion High School jersey with the name “Bryant” on the back as he watched the intersection of two of his favorite sports entities.

He is 51 years old, a Chino Hills resident and went to every single one of Lonzo Ball’s high school games. He didn’t want to miss the start of Ball’s NBA career. He’s also been a Lakers fan since the days when Magic Johnson was playing instead of constructing the Lakers’ roster as their president of basketball operations.

“Very excited,” Appelbaum said when asked how he felt when his favorite team drafted Ball, who is also from Chino Hills. “LaVar said it was gonna happen. I was hoping.”

The Lakers were the late game on Saturday in Las Vegas, the fourth of a series of contests spaced two hours apart starting at 1 p.m. As each game passed, the crowd filled in just a little bit more until, for the day’s finale, the lower bowl was completely packed.

As with any game the Lakers played, the fans leaned significantly purple and gold.

This year’s Las Vegas Summer League Lakers are exciting a fan base looking for some positivity after four years of lacking it. On Saturday they beat the Brooklyn Nets 115-106 in the summer league quarterfinals. Vander Blue scored a game-high 27 points. The Lakers are hoping the positive momentum they are building here carries over into the fall.

“There’s definitely tons of excitement and renewed energy around this year’s draft, around Magic Johnson and Rob Pelinka and the leadership and the vision they’ve cast with the basketball team,” said Joey Buss, Lakers co-owner, alternate governor and vice president of research and development. “I think that positive momentum is carrying over into summer league and that’ll carry over into preseason, training camp and the start of the regular season later this fall.”

Last weekend, Lakers fans helped cause the first sellout ever at Las Vegas Summer League, with 17,500 people buying tickets for July 8, the day the Lakers played the Boston Celtics. The arena filled slowly throughout the day, but was packed by Lakers tipoff. They jammed the arena daily, chanting not just for Ball, but other standout summer league Lakers.

They were so boisterous that during a halftime baby race, an announcer asked the crowd to please not boo a baby wearing a Celtics jersey.

“We have the best fans in the world, we’re close to L.A. here and the Laker fans have really showed up to support the team,” Buss said. “To support ball and support the other draft picks as well.”

Outside of Ball, they’ve seen strong performances from second-round pick Thomas Bryant, from forward Kyle Kuzma, who scored 26 points Saturday against the Brooklyn Nets, and from Alex Caruso, whose performance earned him a two-way contract to play for the Lakers and their development-league team, the South Bay Lakers.

“The Lakers, when they were bringing their teams there was a ton of excitement anyhow,” said Warren LeGarie, an agent who helped create Las Vegas Summer League.

“The fact that they’re bringing high-profile players certainly added a bigger buzz. And the other thing the Lakers knew they had to do was also promote their new additions. Create some optimism. Some hope. These guys were the lifeline to that hope. I think they realize this is really good forum for them.”

Ball’s emergence in summer league has excited the Lakers’ coaching staff and those watching from courtside seats, including Lakers head coach Luke Walton and assistant Jesse Mermuys.

It’s also excited fans. One wore a purple tie-dyed shirt with the Lakers logo on it but the word “Lonzo” where the word “Lakers” normally is. Some fans wore his UCLA jersey. Others had his Lakers jersey on.

The Lakers’ second overall pick had two triple doubles in summer league, and heading into Saturday’s game, he led summer league in steals and assists.

There are no guarantees of how that will translate to the regular season, but the start has offered some hope.

tania.ganguli@latimes.com

Follow Tania Ganguli on Twitter @taniaganguli