John Beilein’s real NBA coaching debut comes in October.

He probably knows a little bit more about what to expect now.

Cleveland’s new coach got his first bit of practice for the real thing on Monday in the NBA’s first game of the summer — only to have San Antonio spoil his debut.

Lonnie Walker IV scored 20 points, and the Spurs beat the Cavaliers 97-89 in the Salt Lake City Summer League opener.

Afterward, Beilein said there’s still some things he had to learn about the NBA game. He thought there was going to be a jump ball to begin the second quarter, only to learn the NBA doesn’t have those.

“We’re all learning right now,” Beilein said. “We weren’t as fortunate as we’d like to be today, but we’re all going to grow immensely from it.”

Drew Eubanks and Quinndary Weatherspoon each scored 13 for San Antonio, which got 11 from Luka Samanic and 10 from Ben Moore.

Walker struggled in his summer debut last year, going 3 for 16 then. He was 8 for 12 from the floor on Monday, and lauded the Spurs’ staff for the work they’ve done with him over the last 12 months.

“It’s an eye-opener,” said Walker, who appeared in 17 games with the Spurs last season after getting drafted following one year with the Miami Hurricanes.

Dylan Windler led the Cavaliers with 19 points.

“I just like the way he moves,” Beilein said. “He instinctively has a really good feel for the game.”

Malik Newman and Naz Mitrou-Long each added 16 points for Cleveland. Mitrou-Long also had eight assists.

Beilein also made the first coaches’ challenge of the summer, an option that teams are likely to have in the NBA this season on a one-year trial pending approval next week by the league’s board of governors.

His challenge of a foul call wasn’t upheld.

“Could have went either way,” Beilein said.

Warriors sign Robinson III

Former Piston Glenn Robinson III reached agreement on a two-year contract to join the Golden State Warriors, giving the team shooting depth next season as Klay Thompson works back from a serious knee injury.

Robinson’s agency, Beyond Athlete Management, said Tuesday that Robinson’s deal includes a player option for the second season.

Assistant coach sentenced

A Boston Celtics assistant coach has been sentenced to probation and ordered to pay a fine for accepting $300,000 in bribes to get a wealthy Florida businessman’s son into the University of Pennsylvania.

Court records show a federal judge imposed the sentence Monday on Jerome Allen, the former head basketball coach at Penn. In addition to four years’ probation, the 47-year-old Allen must pay a $202,000 fine and forfeit another $18,000.

Allen received a lenient sentence after testifying for prosecutors against Philip Esformes in a $1 billion Medicare fraud trial.

Simmons gets $170M offer

As expected, Ben Simmons will receive a five-year, $170 million contract extension to stay with the 76ers.

The Sixers offered the maximum extension to the point guard and his agent, Rich Paul, and the team are working out details, a source confirmed. ESPN first reported the news.