WASHINGTON — Andrew G. McCabe has risen so fast at the F.B.I. that he has become a source of both admiration and resentment. So a favorite way to criticize him is to offer one of the most backhanded compliments in the bureau’s lexicon: He’s a great briefer.

Mr. McCabe’s talent for briefing his superiors is regarded by many workaday agents as nothing more than an ability to discuss somebody else’s work. But it is highly valued at F.B.I. headquarters, and in a city where briefings become policy.

“With McCabe, it was always his capacity to understand an issue at great depth that made him stand out,” said James W. McJunkin, who supervised Mr. McCabe years ago in the F.B.I.’s counterterrorism division. Mr. McCabe provided unvarnished information, he said, with cut-to-the-chase precision.

That ability was on display on Thursday in Mr. McCabe’s first public appearance as acting director, less than 48 hours after President Trump fired James B. Comey, Mr. McCabe’s boss.