Nick Kyrgios is giving it up to the game’s greats in the latest episode of his podcast, No Boundaries.

Kyrgios, who co-hosts the show with friends Alex Babanine and James Frawley, shared a clip from the latest episode of the podcast—which premiered earlier this fall—highlighting the extraordinary efforts of sporting greats like Novak Djokovic and Roger Federer.

“We just take it for granted,” Kyrgios said of the two 20-time major champions in addition to basketball stars Stephen Curry and LeBron James. “When they retire, people will go on about how they were the best, but while they’re playing, it’s always criticism.”

The Aussie goes on to praise Federer in particular, who ended his year after the Wimbledon Championships to undergo knee surgery.

“He’s doing his back in right now in knee rehab, just trying to play for half the fans in the world and himself.”

Kyrgios was last on court to play Laver Cup before also shutting down his season due to a knee injury. A former world No. 13, the 26-year-old appeared to be rounding back into form after sitting out tournaments between the Australian Open and Wimbledon, reaching the third round in singles of the latter and winning a round of mixed doubles with Venus Williams.

Click here to listen to Episode 6 of the No Boundaries podcast.