Michael Avenatti kept his client in total darkness as he maneuvered to shakedown Nike for some $20 million, a witness testified Monday in the lawyer’s extortion trial.

“I trusted that he was going to go to Nike and try and achieve Gary’s goals,” Jeff Auerbach told jurors, referencing his pal-turned Avenatti client Cal Supreme coach Gary Franklin.

Instead, Auerbach testified that Avenatti just kept saying meetings “went great” — while failing to mention a $22.5 million settlement demand, an investigation, threats of a press conference, or even the presence of lawyer Mark Geragos, who was never charged.

Auerbach testified he and Franklin originally approached Avenatti because they thought he would be “diplomatic” as Franklin fought to regain control of his team, but instead were met with “utter shock and horror” as Avenatti violated their trust in the lead-up to his arrest.

“It would be detrimental, damaging and totally averse to meeting Gary’s objectives,” Auerbach responded when asked by prosecutors if Franklin wanted a press conference to expose Nike’s alleged misconduct.

“We were trying to forge a new future,” he said of the relationship between Nike and the coach.

Nike lawyer Scott Wilson previously testified that Avenatti kept threatening that he had reporters on “speed dial” if the company didn’t meet his monetary demands.

“I’ll take $10 billion off your client’s market cap,” Avenatti can be heard saying in a recording made by Wilson, played at trial last week. “This is gonna be a major f–king scandal.”

Avenatti claims he was simply advocating for Franklin — while prosecutors say that can’t be true, since Franklin wasn’t in the loop.

Auerbach’s testimony continues Tuesday.