In one heart-tug to return to his roots, James has reduced the Heat from a team that had gone to four consecutive NBA Finals and won two championships to one that very well soon could be preparing for the lottery.
The Cavaliers, who have missed the playoffs every season since James ditched them in 2010, have been vaulted to the top of the Las Vegas odds, at 4-1, to win the 2015 NBA championship.
Cleveland, as it stands today, is not legitimately the favorite, but no bookie will keep 60-1 odds on a team that has James - especially when upgrades are possible.
This is a butterfly effect and when it is done, the ripple from its wings could alter the makeup of no fewer than 10 franchises.
With James, Cleveland instantly vaults into the upper echelon of the Eastern Conference, but this is about winning the city's first professional sports title since the Browns in 1964.
Even with the most impactful player on the planet and budding star point guard Kyrie Irving, the Cavaliers do not have a championship roster yet.
What you can be sure of is that James would not have left Miami without a commitment from the Cavaliers to upgrade the roster significantly - and quickly.
It was one name James did not mention in his essay announcing the move that made the most noise when he talked about mentoring younger teammates and helping them grow as players and hopefully into champions.
He specifically named Irving, guard Dion Waiters, forward Tristan Thompson and his former/new teammate Anderson Varejo.
Not so conspicuously absent was the name of Andrew Wiggins, the player the Cavaliers drafted No. 1 overall less than 3 weeks ago; you know, the kid from Kansas University who plays the same position as James and was touted by some as the most impressive prospect since James.
Wiggins could be the only person in Cleveland unhappy that James is coming home, because you better believe that sitting in as a 4-year understudy to "The King" is not what the heir apparent or his marketing machine had in mind.
It is not unreasonable to think that Wiggins will be dangled as bait by the Cavaliers to bring in a high-level proven NBA presence to partner with James.
The name most mentioned is Minnesota Timberwolves All-Star center Kevin Love, who won a gold medal with James at the 2012 London Olympics.
Overshadowed in the drama about what James and New York Knicks free agent Carmelo Anthony would do this summer is the fact that Love has not backed away from his stance that he will not re-sign with the team after this upcoming season.
To get any return, the Timberwolves must trade Love, and a package involving the potential of Wiggins would be digestible.
ESPN reported that a source close to situation indicated that Love would commit long-term to the Cavaliers to team up with James. Who wouldn't?
Yesterday, early on in the wake of James' announcement, Cleveland reportedly talked about a package involving Waiters, 2013 top overall pick Anthony Bennett and draft picks for Love, but that rumor was later put to rest. So, if you have James and the Timberwolves say, "Wiggins," will you really let that stop you from acquiring Love and making James happy?
Cleveland's gain cripples Miami.
Even though it is being reported that another member of the former "Big Three" - Chris Bosh - apparently did an about-face and will return to the Heat instead of taking the 4-year, $88 million offer to the join the Houston Rockets, this is not a championship-caliber squad without James.
The Heat got taken apart by the San Antonio Spurs in the NBA Finals with James.
I can see why Bosh would stay in Miami. He has two championship rings and if the offer, as reported, totals $118 million, that extra $30 million will soothe the pain of not winning another title.
I'm not sure why Heat president Pat Riley would sign off on this. Bosh is not a star attraction, and even if oft-injured guard Dwyane Wade were to return to All-Star form (unless he's wooed away by his hometown of Chicago), it won't be enough to keep Miami where it is.
Bosh was worth the money when he was the third piece to James and Wade. Now he will just be a big-ticket item whom Miami will not win another championship with and who will eat up cap space for the next 5 years.
The Rockets may have become just as big a loser as Miami.
Houston was looking to step up to Finals contender by adding Bosh to All-Stars James Harden and Dwight Howard.
The Rockets created salary-cap space to sign Bosh by trading reserve center Omer Asik to New Orleans and yesterday moving point guard Jeremy Lin and a first-round pick to the Los Angeles Lakers.
Now they are faced with either matching the $45 million contract forward Chandler Parson signed with the Dallas Mavericks and tying up their salary cap for the next 3 years or letting a valuable player go to a division rival without getting anything in return.
Houston has until 11:59 p.m. tomorrow to decide. The Rockets are now in worse shape, but have no one to blame. Red flags should have gone off when Bosh told them he'd take their $88 million only if James left Miami.
Turns out James did, and Bosh left them at the altar, anyway. Houston could make a last-second move for free agent Luol Deng, but would be in a bad negotiating position.
Had Bosh come to Houston, the San Antonio Spurs, Oklahoma City Thunder, Golden State Warriors, Los Angeles Clippers and Memphis Grizzlies would all have had to make adjustments to keep Houston from sprinting ahead.
With James now off the market, the focus shifts to Anthony. If he leaves the New York Knicks and goes to Chicago, the Bulls, with Anthony, a healthy Derrick Rose and maybe Wade become the team to beat in the Eastern Conference.
If Anthony stays in New York, new Knicks president Phil Jackson will be active in trying to find ways to upgrade the roster.
The Indiana Pacers have lost to Miami in the last two Eastern Conference finals, but now, with the Heat knocked down, they have to feel as if one solid addition will allow them to exploit the situation into a championship, the way the Rockets did during Jordan's sabbatical.
Other fringe contenders in the East, such as the Washington Wizards and Atlanta Hawks, must be thinking the same thing, and would be foolish not to acquire a dominant player to try to steal the apple before James gets it all together and rolling in Cleveland.
The Prodigal Son is returning home. The rest of the NBA will react to his footsteps.