Fifteen years into his once-in-a-generation career, LeBron James is still hoisting whole basketball teams onto his back, often seeming, especially on offense, to occupy every possible role on the court. This year’s Cleveland Cavaliers, assembled on the fly, midseason, in the heat of a crazily busy N.B.A. trade deadline, stand among the least coherent and least experienced groups he’s played with. And still, thanks almost totally to James, they survived, by the smallest of margins, their first-round playoff series, against the Indiana Pacers. At this point, we’ve seen every trick James has to offer; the continuing shock is just that he’s been at it so long, and looks ready, for the foreseeable future, to keep going. (Up next: the Toronto Raptors, perennially one of James’s punching bags.) But, this year, that shock has been accompanied, for me, by another: for the first time, I can imagine what the league might look like after he leaves.

In the past few years, the N.B.A. has enjoyed an especially impressive influx of young talent at just about every position, yielding a league whose competitive balance has tipped, this season most pointedly, toward young legs and away, ever so slightly, from veteran experience. This year’s contest for Rookie of the Year took on outsize importance, probably because fans saw in the main combatants—Ben Simmons, the nearly seven-feet-tall and yet somehow Houdini-ish point guard for the Philadelphia 76ers, and Donovan Mitchell, the joyous gunslinger, built and wired a bit like a tank, who recently led the Utah Jazz past the Oklahoma City Thunder—a pair of players that might dominate the league for years. Meanwhile, an older group of big names once known as the “Banana Boat” crew, famous as vacation-mates for James, is sliding out of the spotlight: Carmelo Anthony was a total liability, floating airballs like languid paper planes, in the Thunder’s series loss against the Jazz; Dwyane Wade, of the Miami Heat, who lost in the first round to Simmons’s Sixers, mustered the occasional heroic quarter, but more often looked, in the droop of his eyelids and slight limp in his gait, like Bruce Willis toward the end of a “Die Hard” ordeal. Only Chris Paul, from that banana bunch, has successfully reinvented himself, as a Stradivarian second fiddle for James Harden in Houston.

There’s something eerie about the way a new generation simultaneously eclipses and echoes the one that came before it. On the later seasons of “Mad Men,” one of the better plotlines spun around a character named Bob Benson, initially unplaceable and so enigmatically talented, who resembled and, by implication, threatened to replace, Don Draper. That kind of uncanny mimicry helps explain the growing enthusiasm for Simmons, who, during the playoffs, has become LeBron’s Bob Benson, and my favorite player to watch. Simmons is tall and imposing; he can muscle into the paint but is most effective as a passer and playmaker—more incredible, on the court, as an intelligence than as a body. Watching the Sixers’ first-round contest against Wade’s older and more rugged Heat, I thought of LeBron’s 2007 series against the Detroit Pistons, who were then the Eastern Conference’s reigning juggernaut. In that series’ final game, James unspooled a performance for the history books—or at least the better YouTube channels, if that’s how we’re doing things from now on—scoring twenty-nine of his team’s final thirty points. It was a confirmation that James’s previous intimations of greatness were no fluke. Similarly, in Simmons’s last game against the Heat, his already formidable control seemed all but complete. During one possession in the third quarter, he loped up-floor, typically unbothered, then, from the three-point line, with an underhand flick of the wrist, lobbed the ball in a tight ellipse toward the basket, where his extraterrestrially dextrous teammate Joel Embiid was already airborne and available to flush it home. This is the sort of casual virtuosity we have come to expect from James, and, for that reason, it was almost reassuring: the game has surely changed, and even its greatest personnel will fall away, but here we have something to look forward to down the road.

Now Simmons, Embiid, and the Sixers face another youth-fuelled unit in the Boston Celtics. After losing Kyrie Irving to injury—at twenty-six, Irving’s pretty young himself—the Celtics have relied on the fresh-faced tandem of Jayson Tatum, a rookie, and Jaylen Brown, a second-year player. Neither Tatum nor Brown has as obvious a forebear as Simmons has in James, but their self-possession in the postseason has been just as impressive. Brown recently became Boston’s latest victim to injury, and his load has been picked up, in part, by the twenty-four-year-old guard Terry Rozier, whose renown is so new that one of his opponents in the last round pretended not even to know his name. Already, the Celtics have offered a stouter challenge for the Sixers than the Heat did. Last night, on the way to a 117–101 victory in the first game of the series, they used their uncommon athleticism to chase Philly’s sharpshooters—J. J. Redick, Ersan Ilyasova, and Dario Šarić—away from the three-point line, and out of the rhythm that they’d established against Miami. In order to overcome them, Simmons will have to draw on powers not unlike those displayed by LeBron against the Pacers—or, at least, I hope so.