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.

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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,

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