“I believe we were a little bit lucky at the beginning of the season that we played well, and always the beginnings are tough after injuries,” Nadal said. “You need to win these kind of matches that change the confidence, change the feeling, and that’s what happened. The important thing is the body holds up.”

Federer said that the back problems that hampered him during the North American hardcourt season this summer were, for now, not an issue, and that he definitely needed a rest. This is not much of one.

He was practicing in Prague less than two weeks after he lost in the quarterfinals of the United States Open to Juan Martín del Potro, who pulled out of the Laver Cup because he felt he had not yet recovered (his absence further slims Team World’s already meager chances).

But Nadal, who arrived in Prague little more than a week after winning the U.S. Open, said he felt the Laver Cup, where matches will be best-of-three sets with a super-tiebreaker instead of a full third set, was worth a quick turnaround.

“We are creating something big,” he said. “We are together in the same team, so it’s all about the personal energy and the personal feeling you have, and here we have the feeling we are getting in a place where we really want to play, because we are doing something exceptional, something that never happened. And I’m very excited, so it doesn’t matter if I’m tired, if I’m coming from the U.S. Open or we’re playing for a long season.”

Nadal and Federer, both driven from within, are playing this well again in 2017 in part because of each other. Would they have achieved so much for so long without the other to provide motivation?

“In some ways I believe yes, and in some ways I believe no,” Federer said. “I believe that because of Rafa, maybe I achieved less, but at the same time, I feel like he made me a better player.”