The American has now doubts about who is the best returner in tennis. Who is the best returner in tennis? Well, the best server in tennis has his opinion, and it’s a strong one: Novak Djokovic.

After his 6-4, 6-3 loss to the Serb on Monday in London John Isner threw this heavy praise on the World No.1.

For those scoring at home, here is the original transcript:

Q. You seem to serve pretty well tonight on the whole, I thought. In terms of the best returners you have ever faced in your career, where do you rank Novak? Do you rank him as the best?

JOHN ISNER: Yes, he is No.1 and No.2 and No.3. He’s the best returner I’ve ever faced for sure. I’ve said that before, too. So he’s a very good tennis player.

Isner also went on to say he got his “ass kicked” by Isner and continued to praise the Serb.

“From the first point of the whole match he connected pretty well on a return,” he said. “But I mean, to be honest, I’m not surprised. Sometimes you got to hope he’s a bit off. Unfortunately, I don’t think that was the case tonight. I got my ass kicked. That was pretty comprehensive out there.”