With Boston’s impressive win in Game 5 on Tuesday night, the series has once again swung the Celtics’ way, and they have a chance to close out the Cavs in Game 6 on Thursday.

Has there ever been more riding on a conference semifinal playoff game?

While there are those that believe LeBron James is more likely to leave Cleveland if the Cavs were to win the title, the general consensus is just opposite. If the Cavs suffer another pre-Finals flame out, most NBA fans believe that LeBron will sign elsewhere this summer.

But it’s not like LeBron had one of his monster near-triple-double games and his teammates let him down. The other Cavs shot 46% from the field, 45% from 3PT and hit 18-of-22 free throws. Shaquille O’Neal posted 21-4 (hitting 7-of-10 free throws) along with four blocks.

Meanwhile, LeBron shot 3-of-14 from the field (0-4 from 3PT) and scored just 15 points. For the first three quarters, he settled for long jumper after long jumper and missed most of them. Once again, his unwillingness to go in the post limited his options in a game when his jumper just wasn’t falling. Two of the game’s great wings — Michael Jordan and Kobe Bryant — made/make a living on the block, especially when they were having trouble scoring elsewhere.

Defensively for the Cavs, it was another story.

There were times in the third quarter that Mike Brown looked like his life was flashing before his eyes. The Celtics shot 55% from the field, but the guy who spearheaded that hot shooting night — Ray Allen (8-for-13. 6-for-9 from 3PT) — hit some tough shots. The bottom line is that the Cavs are having trouble hiding Mo Williams defensively. When he’s on Ray-Ray, they run him off of screens until Allen gets an open look. Rajon Rondo just takes him to the hole. (Maybe more Delonte West is in order?)

When the Celtics weren’t going after Williams, they were feeding the ball to Kevin Garnett on the block. Since last year’s playoff loss to the Magic, the Cavs were so worried about matching up with Orlando’s “stretch 4″ — Rashard Lewis — that they forgot about Garnett’s ability to hit the turnaround over Antawn Jamison in the post.

Now I’m not writing the Cavs off. They came out with a vengeance in Boston in Game 3 and they are perfectly capable of doing it again. I fully expect a great performance from LeBron in particular.

But what if the Celtics close out the series? What happens then?

Suddenly, LeBron is in play for a number of teams, namely the Knicks, Bulls, Nets, Heat…who knows, maybe even the Clippers. It would throw Dwyane Wade’s summer into question. Right now, it looks like he’s staying put and hoping that a power forward will join him in South Florida. But if LeBron is on the move, maybe Wade would join forces with him in New York, or maybe he’d convince him to come to Miami. Suddenly, instead of being the top free agent option for the Heat, Chris Bosh has to wait for LeBron to make up his mind. All the way down the line — Amare Stoudemire, Joe Johnson, Rudy Gay, David Lee — everyone would be affected.

If LeBron does change teams, it would alter the NBA landscape forever. Remember, he’s 25 and is just now getting into his prime. Whoever is lucky enough to sign LeBron will likely get the best that he ever has to offer. And we’re talking about a guy who has already won two MVP awards.

This is not just another playoff series. The final score of Game 6 could reverberate for a long, long time.

Photo from fOTOGLIF

John Hollinger writes in his latest PER Diem (Insider subscription required) that LeBron’s best bet for long term success may not be in Cleveland…or New York…or New Jersey/Brooklyn…

And it’s especially worth noting that if the Cavs are back in the 45-50 win range this season, King James might be a much more portable commodity this coming summer. If he’s looking at a Cleveland lineup with one majestically talented player and several spare parts, one would think the comparison to such arrangements in New York or New Jersey wouldn’t be dramatically different.

But those aren’t close to being the most palatable changes of uniform available. For instance, it bears mentioning that joining the Chicago squad LeBron’s team lost to Thursday night would be dramatically different. With a young star point guard, quality big men and lots of secondary help, the Bulls — who could get as much as $20 million under the cap if John Salmons opts out of his contract, conveniently opening a spot in the lineup for LeBron at the same time — would offer a more clear opportunity for long-term success.

Let me throw out an even crazier proposition — Minnesota. The Wolves will have the cap space to make a run at LeBron, depending on a few variables — or at the very least can get there fairly easily if they know there’s a chance for a player of this caliber. (Declining an option on Ryan Gomes, for instance, is done much more easily if it allows you to replace him with the best player in the league.)

Minnesota is generally thought of as one of the NBA’s least-desirable relocation options, but let’s consider it from a winning perspective. Who would you rather play with for the next five years: Al Jefferson or Anderson Varejao? Kevin Love or Ilgauskas? Ricky Rubio or Mo Williams? Jonny Flynn or West? Ramon Sessions or Daniel Gibson? Next year’s fourth pick or next year’s 24th? It’s obvious, isn’t it?

Don’t get me wrong — the T-Wolves would be a good fit for LeBron, but he’d be a pretty good fit anywhere. I just don’t see him taking his show from one cold, small-market Midwestern city to another cold, small-market Midwestern city. If he doesn’t stay in Cleveland, then there seem to be three real options:

1. Brooklyn Nets
With Devin Harris and Brook Lopez locked up for the next few years, the Nets have two All-Star caliber players already on the roster at two of the toughest positions to fill — point guard and center. Is the penetrating Harris the perfect fit alongside LeBron? Not necessarily, but if the Nets can find a sharpshooting off guard (Courtney Lee?) and face up power forward (a la Rashard Lewis), the Nets would really be in business. Plus, the move to Brooklyn would take away the stigma of playing in New Jersey.

2. Chicago Bulls
It would break the city of Cleveland’s heart if LeBron fled to the Windy City. New York or Brooklyn? Cleveland fans wouldn’t like it, but they’d understand. But if LeBron heads to Chicago, home of the team that stepped on the Cavs’ throats so many times during the Jordan era, the city might explode. From a pure basketball point of view, it’s a nice fit. They already have Derrick Rose, Luol Deng, Joakim Noah, Kirk Hinrich and maybe Tyrus Thomas. Chicago is also a threat to pry Dwyane Wade out of Miami.

3. New York Knicks
This is more about MSG and the spotlight than who the Knicks have on the roster. Playing in Mike D’Antoni’s system would be nice, and if the Knicks can unload either Eddy Curry or Jared Jeffries, they’d have enough cap space to sign another free agent to max deal. This might be a case of the Knicks having to coax Chris Bosh out of Toronto or Amare Stoudemire out of Phoenix before being able to convince LeBron to sign on the dotted line.

We’re only a couple of weeks into the season and the talk is already starting. The Cavs have plenty of time to morph into a 60-win team, but right now they don’t look it. And the longer they struggle, the louder the drum beat is going to sound.