Deputy Attorney General Rod Rosenstein heaped praise Friday on newly announced acting Attorney General Matthew Whitaker.

Speaking to reporters Friday at a investiture ceremony for U.S. Attorney Zachary Terwilliger in Alexandria, Va., Rosenstein said Whitacker, who was chief of staff to newly exited Attorney General Jeff Sessions, was a "superb choice."

"I think he's a superb choice for attorney general," Rosenstein said. "He certainly understands the work, understands the priorities of the department."

Not everyone bought the comment, including former CIA Director Michael Hayden, a vocal critic of President Trump. "Repeat the lie often enough until the lie becomes the truth. And then good people defend the lie," he tweeted in response.

Trump announced Whitaker's new role on Wednesday. "We are pleased to announce that Matthew G. Whitaker, Chief of Staff to Attorney General Jeff Sessions at the Department of Justice, will become our new Acting Attorney General of the United States," Trump said in a tweet. "He will serve our Country well."

As a stand-in for Sessions, Whitacker will have oversight of special counsel Robert Mueller's Russia investigation. He has faced criticism for past comments he made about Mueller and the scope of the inquiry, and has been pressured to recuse himself from overseeing the probe.

Rosenstein had been charged with overseeing Mueller's operations ever since Sessions recused himself from it last year — a point of contention between him and his former boss, Trump.

Asked by ABC News' Mike Levin whether he was worried about Mueller's investigation now, Rosenstein didn't answer and walked away.