It was the rigorous conditioning test the Heat put players through before training camp that is legend within the league. Some athletic trainers claim it's the most demanding such test in all of the NBA or NFL.
For some players, it takes months to get ready for.
To be admitted to training camp, a player has to run the length of the court 10 times in under a minute. Then two minutes recovery. Then again. Two minutes recovery. Then again. And again. And again.
It's so fierce that by the time he was a multi-time champ, Dwyane Wade pulled rank and opted out of it every fall.
Just as Butler's first try was set to begin, Pat Riley, team president and franchise godfather, appeared on the sideline. Butler saw him, his adrenaline immediately pumping.
For the first several rounds, Butler was flying through the drill. But by the fifth round, his back stiffened; he'd gone too hard. When it was over, Butler had failed.
The next morning, Butler was up before 4 a.m., going back into the gym getting ready to try it again. As he did so, he was almost afraid to look at his phone. He could see the headline, "$140 million max player fails conditioning test."
It didn't come. The Heat kept it quiet; they didn't want to shame him. They wanted to support him.
But his 4 a.m. practices became public. And within days teammates were joining him, tweeting their arrival at the gym at 3:30 a.m.
Butler never felt so much at home.
It's hard to explain how much Riley and head coach Erik Spoelstra love Butler. They've had a few players like this over the past 25 years.
Alonzo Mourning. Tim Hardaway. Wade. Udonis Haslem.
But never have they fallen faster and harder than they have for Butler, the type of hard-nosed, team-focused, no-nonsense leader they would create in a laboratory if they could. Even Wade, who has taken on a sort of captain emeritus role, is smitten.
"[Wade's] always in my phone, telling me about the game, what to look for," Butler said. "He's been a huge help. He's the first person that texts me tonight whenever I get back to the locker room."
Spoelstra, who barely blinks or sleeps when he gets into playoff mode, was stoic on the sidelines Monday night. Riley, attending his first game in the Florida bubble, was seated in the upper deck. But their hearts were probably leaping in their chest when they saw Butler put in 15 fourth-quarter points as the Heat beat the top-seeded Milwaukee Bucks 115-104 to take a 1-0 lead.
"He just fits everything about us, our fabric and who we are," Spoelstra said. "These are extreme circumstances, they're not easy for anybody. And you need a level of discipline, of structure, and camaraderie. Jimmy, despite what, probably, the narrative is out there, he's a very likable guy in the locker room, and I think that helps in a setting like this."
Let's be clear. There are times when Butler rankles his teammates, his coaches and his front office. And there are times when they do so to him. In the past, these moments have sometimes defined Butler.
Two teams traded him. Another, the Philadelphia 76ers, didn't prioritize keeping him. That's the resume of a journeyman not a superstar.
The difference is that the Heat, led by Riley's long-honed principles for team building, don't mind a little friction. They even welcome a reasonable dosage of it, because handling it and moving on is productive. Riley, and by extension Spoelstra, believes it can sharpen senses, deepen bonds and create trust.
The Heat played like a team that trusted Butler unconditionally in Game 1. Even though he'd played through a shoulder injury at the end of the quarterfinals against the Indiana Pacers, he looked rested and healthy while pouring out energy at both ends of the floor, finishing with a playoff-career-high 40 points.
Defensively, Butler fought through screens, challenged shots and chased Bucks everywhere. On offense, he challenged Milwaukee's famously tough interior defense, repeatedly darting into the paint to draw fouls. Butler drew nine fouls and earned 13 free throws, a vital part of the Heat game plan. Overall, the Heat outscored the Bucks by 11 points off of free throws.
The rest of Butler's teammates, from rookie Tyler Herro to veteran Goran Dragic, fed off of him. Their team defensive energy and fidelity to the game plan of clogging Giannis Antetokounmpo's driving lanes worked.
In the fourth, it was a stream of Butler jumpers that slammed the door on the comeback win. Relying on Butler to make such shots isn't the best strategy; he had a relatively poor shooting season. But the Heat know they can rely on Butler for something every game, and he made all four of his field goal attempts outside of the paint in the fourth quarter of Game 1, including his second 3 of the night.
Worrying about failing has long since left Butler's mind.
"Confidence for us comes from what we do every single day," Butler said. "We work so hard, we practice like we're supposed to practice, we study film like we're supposed to study film. That's what we bank on every single second of every game. There are no nerves in this because we are so confident we are working to be great, not just good, great. So we have that in our corner."