DoubleLine Capital CEO and “Bond King” Jeffrey Gundlach gave Federal Reserve Chairman Jerome Powell a “C-minus” grade because of his waffling stance, which reminded him of a losing NFL coach.

“He just says, ‘data-dependent; don’t know what we’re going to do; we might.’ He basically wants to say as little as possible.”

In the Yahoo Finance interview that covered a wide range of topics, Gundlach said he was frustrated with the Fed’s flip-flopping.

“Every press conference from basically December until about June was a completely different message from the one before,” Gundlach said. “And they were getting increasingly dovish. And then he kind of went all-in on dovishness, and started to follow the bond market and cut rates.”

Gundlach ripped into Powell calling him “an NFL coach after losing a game.”

“(Those coaches) all say the same thing, ‘Got to watch the tape, got to play better, not good enough.’ Now Jay Powell does the same sort of boilerplate. He just says, ‘data-dependent; don’t know what we’re going to do; we might.’ He basically wants to say as little as possible.”

The billionaire continued to slam the Fed for “shamelessly following the bond market (more) than ever before.”

Outside of Paul Volcker’s tenure, Gundlach noted that the Fed has always followed bonds when negotiating interest rates, which has led him to not grade the Fed or Powell favorably.

“So at this point, I’m afraid I would have to give Powell a pretty low grade. I’d give him a C-minus because of the fact that he’s really kind of lost his way as it appears.”

He also sees Powell “leading the way for kind of cheerleading inflation higher, which is probably one of the reasons why bond yields have risen kind of globally and in the United States as well.”

This would all be music to President Donald Trump’s ears, who makes attacking the Fed and Powell one of his regular pastimes. But Gundlach differs from the president when it comes to one thing: negative interest rates.

Gundlach said Powell would probably get a D or even D-minus if he embraced negative interest like Trump has repeatedly called for him to do.

“(I) strongly and loudly applaud his statement that he doesn’t think we should take interest rates negative in the United States,” Gundlach said.

“Because if the United States went negative with Japan and with Europe negative, I think it would be fatal to the global banking system because there’d be nowhere for capital to go.”