The arrests of two well-known NBA figures Thursday in a nationwide federal investigation into internal gambling and high-tech scam poker — especially a sitting head coach and former Finals Most Valuable Player — have roiled the league, from players to front offices to agents, sources told NBC News.

The arrests, particularly that of Hall of Famer and Portland head coach Chauncey Billups, altered the tenor of this week’s conversations around the NBA, whose new season had started only two days earlier.

The mood, a front office executive for one team said, went from fanfare to “fear.”

“Who else is involved?” the executive said. “It’s a nightmare for the league.”

Reactions to the extraordinary news spread quickly, ranging from surprise to anger at the league itself, according to five people

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