That much was clear during the second overtime period in a Jan. 10 loss to the surging Brooklyn Nets, as the two-time defending champs were outscored 15-6 in what quickly became an extra-time rout.
But the reigning MVP was talking about more than just those final handful of minutes. According to CBS Sports' Ken Berger, LeBron said the entire season is an arduous process:
It's a long and grueling season for all of us, not just us because we're the champs. We've played a lot of basketball in our four years together. It's taken a lot of wear and tear on all our bodies. It's mentally fatiguing. And you just try to find the motivation the best way you can as an individual and as a collective group.
This type of sentiment can't be a reaction stemming from one disappointing loss, even if LeBron played 49 minutes before fouling out during the first overtime period. It's clearly something that the NBA's premier superstar has been weighing for quite some time, and it's a thought that makes a great deal of sense.
From a sheer numbers perspective, Miami has played more basketball than any other team in the NBA since LeBron took his talents to South Beach.
They've played in each of the last three NBA Finals, even though they lost to the Dallas Mavericks in the first attempt at a championship.
Twenty-one playoff games were added to the regular-season total in 2010-11. Another 23 were played during the 2012 postseason, and it took Miami 23 more to hoist up the Larry O'Brien Trophy last year. That's an additional 67 games, which is more than many guys play throughout the length of an entire regular season.
For perspective, only 200 of the 469 players who suited up last season, per Basketball-Reference.com, hit the 67-game mark.
And again, that's only from a numbers perspective. It doesn't include the time James spent with Team USA during the Olympics. It says nothing about the grueling nature of defending a title, then aiming for a three-peat.
Intensity is needed when every team pictures a bull's-eye on the back of your jersey.
This may seem like a non-story, as the Eastern Conference is so incredibly weak that the Heat can sleepwalk their way through the regular season, emerge from their somnambulant state during the playoffs and still wait until the Indiana Pacers square off with them to truly turn on the jets.
However, it's not, and here's where we hand things off to NBC Sports' Kurt Helin:
But Jeff Van Gundy harped on the key point of those lapses during the Friday night broadcast—is Miami building the good habit during the regular season that they will need come the playoffs? There were questions about that last season but they were able to knock off a Spurs team that certainly did execute. Those issues seem larger this season, however.
It's a valid concern, but it still shouldn't cause either the Miami players or their fans to stay up at night, fearing the nightmares of an early postseason exit that sleep would certainly bring.
How much does the Heat's exhaustion concern you?
This is still one of the most talented teams in the Association, and it'll inevitably have two postseason series to break any bad habits it might have formed during the regular season. It's not as though any of the non-Indiana teams in the East can challenge the Heat over a seven-game series.
Fighting this exhaustion and remaining healthy is priority No. 1 in Miami.
Even if it means losing out on home-court advantage. Even if it means facing inevitable criticism from the media. Even if it means failing to form good habits.
Exhaustion, after all, is one of the few things that can keep this team from the coveted three-peat.