MIAMI (AP) — As a new NBA season opened this week, coach Rick Carlisle and the Indiana Pacers received their annual league-mandated briefing on the do's and don'ts of gambling. Betting in casinos is generally allowed. Betting on other sports, provided it is legal, is also allowed. For veterans of the sport, it's the type of training that can seem routine — almost boring, perhaps. But the potential repercussions for breaking the rules are now abundantly clear after Portland coach Chauncey Billups and Miami guard Terry Rozier were among nearly three dozen people arrested Thursday for what federal law enforcement officials described as their involvement in various illicit gambling activities. “My initial reaction was I was deeply disturbed,” Commissioner Adam Silver said on Amazon Prime Video, during the streaming service’s first broadcast — Boston at New York — on Friday night. “There’s nothing more important to the league and its fans than the integrity of the competition. I had a pit in my stomach. It was very upsetting.” The developments pose an unexpected challenge for a league that hoped to begin its season on a strong note, fueled by an opening night game watched by millions as it went into a thrilling double overtime. There have been amazing performances already: Victor Wembanyama scoring 40 points in his season debut with San Antonio, reigning MVP Shai Gilgeous-Alexander scoring 55 points for Oklahoma City, Golden State's Stephen Curry and Denver's Aaron Gordon putting on an I-can-top-this show. Those should be the talk of the league right now. That's not the case. All that has been overshadowed. The NBA now faces questions about the pervasiveness of gambling in basketball, and uncertainty about what might happen next. “A shocking day,” said Carlisle, who said he unsuccessfully tried to connect with Billups to offer support. “This is a very serious situation.” Rozier, who was arrested in Orlando, Florida, where the Heat opened the season against the Magic, stands accused of telling an associate that he was going to play sparingly in a game on March 23, 2023, when he was with the Charlotte Hornets. Rozier played just under 10 minutes and fell well short of many of the lines set for prop bets regarding his performance. More than $200,000 worth of wagers were won, federal officials said, based on the information Rozier shared. Billups — a Hall of Fame player — was arrested in Lake Oswego, Oregon, and charged with being involved in a poker scheme that federal officials said cheated victims out of at least $7 million. Billups was one of 31 people arrested on the poker-related charges, and some of those arrested were, according to officials, members of three Mafia families.