With LeBron looking mortal, the Warriors looking unstoppable, and the Celtics emerging as a long-term threat, James's future as the NBA's alpha male is suddenly in question. Where does the King go from here?

"What if LeBron never wins another NBA title?" The question isn't new. But for most of the past eighteen months, ever since Kevin Durant signed in Golden State, it's only been whispered. When someone actually says it out loud, in the middle of a basketball debate, it's like throwing a live grenade into the conversation. Everyone would prefer to tread lightly with LeBron skepticism—in part because most basketball fans deeply regret the folly of their LeBron clutch takes in 2011, and also because it's just not very much fun to play the skeptic at this point. LeBron is unbelievable. We'll be talking about his career for the next 50 years. Deep down, everyone is rooting for the story to get as ridiculous as possible. And yet, in spite of that goodwill, or maybe because of it, the third-rail rings discussion is becoming harder to avoid. It might be what defines this NBA summer.

First, there is the Eastern Conference finals. Tuesday in Boston began according to script. At 10:30 a.m. when reporters entered Cavs shootaround, James was on the far side of the court, shirtless, shooting, and drenched in sweat. After a relatively passive Game 1 for LeBron, the whole basketball world was ready for a massive Game 2 response. So, solitary shooting nearly twelve hours before tip-off dovetailed perfectly with the fan fiction everyone was writing for Game 2 as soon as Game 1 ended.

About 30 minutes away, at Boston's shootaround in Waltham, Brad Stevens was clear-eyed about what was coming. "You could go through the career of every great player ever," Stevens said. "They always respond. They're always anxious to respond. They're ready to respond."

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And LeBron responded. He scored 21 of Cleveland's 27 points in the first quarter. This was not a "feel-out game." He bullied Jaylen Brown for a layup, and then a few minutes later, he bullied Marcus Morris to get to the line. Marcus Smart held his own for about 10 seconds, refusing to budge an inch in the post, eventually pushing James out to the three-point line. Then James hit a turnaround fadeaway three as the shot clock expired. It was that kind of night.

The Cavs were up seven at halftime. Four minutes into the third quarter, Marcus Morris hit a three to make it a two-point game. On the very next possession, LeBron James drained a three from the wing to put Cleveland up five. A few minutes later, Morris barreled into Tristan Thompson for a three-point play to tie it. Rolling on the floor, Morris screamed in Thompson's face. Scuffles ensued. The Garden went insane. And LeBron followed that sequence with a running floater from the stripe to calmly retake the lead. Again, that kind of night.

And then it wasn't. The Celtics kept coming. Terry Rozier took over the third quarter, and then Al Horford owned the fourth. Through it all, Marcus Smart was throwing his body all over the floor and inciting exactly the sort of chaos that makes the Celtics machine run smoothly. Smart's been doing this the entire playoffs. He's been so good that he's probably forced millions of people who aren't basketball bloggers or NBA coaches to utter the phrase "winning plays" without irony. And in the middle of the Rozier and Smart storm in that third quarter, the Cavs collapsed. LeBron couldn't do it by himself.

"You've got to tip your hat to LeBron," Smart said afterward. "We knew coming into this game that he was going to come out and give everything he had and he was going to have a game like this. Our job was to just keep going, make it tough on him all night. Eventually those shots he was hitting in the first half, in the second half, stopped falling. And it took a full team effort, everybody off the bench, and guys we just kept sending at him."

Boston Globe

The Cavs will go home for Game 3 Saturday night. The series certainly isn't over. But LeBron hasn't been down 0-2 in an Eastern Conference playoff series in 10 years. He just went for 42 points, 10 rebounds, and 12 assists, and he lost by double digits. Ty Lue is getting outcoached. J.R. Smith has been awful. Kevin Love and Kyle Korver have been uneven. George Hill hasn't shown up. None of this is necessarily hopeless, but it doesn't look great.

Now look more globally. On Monday night the Warriors went into Houston and dominated a Rockets team that won 65 games this season. Kevin Durant has never looked more unstoppable. Meanwhile, the Celtics are emerging as the most compelling long-term threat to everything that's happening in Golden State. Beyond Boston, Houston and Philadelphia still have more long-term weapons than anything Cleveland can bring to the table.

In any "What if LeBron never wins another title?" conversation for the past year, LeBron was generally insulated from criticism. Durant broke the competitive landscape in the NBA. As far as legacy scorekeeping is concerned, losing a title to a team with four Hall of Famers probably won't be held against anyone. Even after Durant's spectacular Finals last year, right or wrong, everyone concluded that Golden State was the best team and LeBron was still the best player. But now we're seeing additional contenders that leave LeBron looking mortal. It's harder to rationalize those failures.

Boston isn't going away, and beginning next year, the Celtics should be much better. Same with the Sixers, a team that beat the Cavs twice in the final month of the season. Houston beat Cleveland by just four points in November, but won by 32 when the two teams met in February. All year long we've been waiting to see the Cavs flip the switch, and except for 10 days against a crumbling Raptors team, it hasn't happened.

That brings us to this summer, obviously. LeBron could go to Los Angeles to try to play with Paul George and Brandon Ingram. He could sign with Philadelphia and bank on a Kawhi Leonard trade that creates that closest analog to the Monstars lineup the NBA has ever seen. He could stay in Cleveland and try to get help from George and Boogie Cousins. Hall of Fame salary cap gymnastics are never out of the question with Daryl Morey, and therefore the Rockets are in the mix as well.

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What's interesting is that none of the free agency options look like obvious solutions to the Warriors problem. Some of those hypothetical superteams wouldn't necessarily be good enough to beat a healthy Boston team, either.

If the Raptors series made the Jordan-LeBron debate realer than ever and reminded the world that LeBron is the most dominant player of this generation, the Celtics series is a reminder that we don't know how this story will end. If there are no moves left to continue making the Finals every year, LeBron won't own the center of the sport for much longer. It's possible that this Boston series marks the beginning of his NBA mortality. If so, it would be a nice bookend to the Eastern Conference finals in 2012, when LeBron played the best game of his career and his reign began.

Maybe that kind of game is what's coming this weekend, and the Cavs will go on to win this series from there. Or maybe this summer LeBron will team with Kawhi in Philly and we'll spend the next 10 months waiting for a legendary showdown with the Warriors. But there's also a possibility that LeBron's entering a new phase of his career, one in which we begin to appreciate him differently than Jordan.

LeBron's mortality could ultimately heighten appreciation for humanity that Jordan never had. Instead of focusing on titles and dominance, we'll focus on technical excellence, social awareness, and the myriad ways James has empowered his peers and made the entire sport more interesting to follow. Of course, he could also continue to demand new help every year, leave teams handicapped by refusing to commit to their future, and jeopardize his goodwill by monopolizing the spotlight with melodrama. That's possible, too. But in any case, we're not there yet.

Sitting next to Kevin Love at the podium after the loss Tuesday, LeBron was asked about the challenge he's facing through the rest of this series. "How will I digest it?" he answered. "I'm going to go home tonight and see my three kids. See my family. Recalibrate. See my mom. I think I'll be fine. I'm not going to lose sleep over it. You go out and when you lay everything on the line, at the end of the day, you can live with that. I'll recalibrate as far as how I can help this team continue to be successful, how I can do some things to make us be even more complete."

While he explained himself, Kevin Love was next to him, laughing with a Cavs beat writer who was threatening to ask Love his first question of the press conference. LeBron picked up on it, and at the end of his answer he added, "The only way I won't get no sleep tonight is if Kev don't get asked a question." The room broke out in laughter, and on cue, Love was asked to diagnose the struggles of Cleveland's supporting cast.

That moment was a good reminder of how LeBron has changed over the years. He's more comfortable with himself. He's capable of laughing at all of this, and so are we. This isn't 2011 anymore. But the Celtics aren't going away in 2018, and neither are the Warriors. LeBron has left no doubts about his place in history, but this year and beyond, there has never been more room to doubt his chances on the court. To paraphrase Brad Stevens, all we know for sure is that a response is coming.