[Weitzman] Harden and Durant, according to multiple Nets sources, butted heads during the season – Durant didn’t think Harden was in peak physical shape, and told him as much.

First, there was the whole Kyrie Irving vaccination mess. Also, Harden and Durant, according to multiple Nets sources, butted heads during the season – Durant didn’t think Harden was in peak physical shape, and told him as much; Harden, meanwhile, struggled to adjust to an ecosystem where everything was no longer catered to him. According to a friend, Harden also became frustrated with the Nets training staff and its focus on maintenance, rest and recovery; after all, in Houston he'd run stadium stairs and lift – even after games sometimes – and he never got hurt.

“I don't mean to, like, just down talk to anybody or whatever. It was just, there was no structure and even superstars, they need structure. That’s what allows us to be the best players and leaders for our respective organizations,” Harden said.

“I just feel like,” Harden continued, “internally, things weren't what I expected when I was trying to get traded there. I think everybody knows that. And I knew people were going to talk and say, ‘You quit’ and all that stuff, but then the following summer, the other superstar there [Durant] wanted to leave. So it’s like: Am I still the quitter?”

Source