When it came time to cast the NBA’s marquee Christmas showcase, basketball’s most storied rivalry — Lakers versus Celtics — was ready and waiting.

The league rarely needs an excuse to hype the blue-blood matchup, but splashy moves over successive summers had landed Kyrie Irving in Boston and LeBron James in Los Angeles. A new-era version of Russell/Wilt or Bird/Magic had fallen into the schedule-makers’ laps. What better way to generate holiday ratings and bicoastal buzz than to pit the estranged former Cleveland Cavaliers teammates against each other?

But when the NBA released its Christmas schedule in August, the Lakers had drawn the Golden State Warriors, with whom they share a state and yellow jerseys, but little else. While the Lakers and Celtics have long been linked by their synchronized greatness in the 1960s, 1980s and 2000s, the Lakers and Warriors have operated more like a seesaw. When one (usually the Lakers) has been up, the other (usually the Warriors) has been down.

Both franchises migrated to California in the early 1960s, but their stories diverged almost immediately. The Lakers and Warriors have won 50 games in the same season just once, in 1972, and they have faced off in the playoffs just twice in the three-point era.

During L.A.’s “Showtime” heyday, Golden State endured six straight losing seasons. When Shaquille O’Neal and Kobe Bryant ran off a title three-peat, the Warriors won just 57 games combined from 2000 to 2002. And when Bryant paired with Pau Gasol to win titles in 2009 and 2010, Golden State was lottery-bound yet again.

Along the way, the Lakers became the NBA’s most glamorous and despised franchise, earning widespread respect for Dr. Jerry Buss’s stable ownership and inspiring envy with their magnetic big-market appeal for superstars like O’Neal. By contrast, penny-pinching Warriors ownership groups forced their die-hards to settle for cult heroes such as Tim Hardaway, Jason Richardson and Baron Davis, rather than champions.

As the Lakers played to celebrity crowds in the “Fabulous” Forum and then unveiled the glittery Staples Center, the Warriors bounced around multiple San Francisco locations before settling into Oakland’s Coliseum. When the aging arena, now known as Oracle Arena, underwent renovations in 1997, the Warriors were displaced to San Jose for the entire season. Who could picture Magic Johnson toiling in Anaheim to accommodate a building makeover?

Of course, this big brother/little brother dynamic has turned upside down over the past five years, as Golden State claimed three titles in four seasons with new owners Joe Lacob and Peter Guber, Coach Steve Kerr and two-time MVP Stephen Curry. Meanwhile, the Lakers bottomed out in the aftermath of Buss’s 2013 death, as his children squabbled in court and cycled through coaches during Bryant’s slow fade into retirement.

In 2016, the Warriors enjoyed the greatest regular season in NBA history (73 wins) as the Lakers endured their worst season ever (17 wins). That summer, Golden State landed Kevin Durant, the biggest free agent on the market, eliciting waves of protests from rival fan bases. The Warriors delighted in their newfound California supremacy — toying with the “Lob City” Clippers and the rebuilding Lakers — and laid plans for the luxurious Chase Center, which will open in San Francisco next season. The franchises’ role reversal was complete.

But James shook the new status quo when he signed a four-year deal with the Lakers in July, giving L.A. fans hope for the first time since Bryant’s retirement and laying the groundwork for what could become the NBA’s next battlefield.

For starters, James brought to L.A. his significant legacy and his long personal history with the Warriors, which includes four straight Finals showdowns. Throughout his prime, he has been stronger, faster, smarter and more skilled than all his contemporaries, and he has made superteam-building into an art form. Yet the Warriors, with their two MVPs and deep lineups of versatile defenders, have beaten him at his own game. If James fails to match Michael Jordan’s six rings, the Warriors will be the chief culprits — weighty stakes that hang over every meeting.

Slowly but surely, James’s arrival has buoyed the Lakers’ confidence and prompted the barbs that help make a great NBA rivalry. “We’ll be champions before you know it,” Bryant mused in early December, according to ESPN. “Then we’ll just be laughing at all the Warrior fans who all of a sudden came out of nowhere.” A few days later, Durant suggested to Bleacher Report that many stars wouldn’t want to join James in L.A. because of the “hype” he generates. “The beat writers just fawn over him,” Durant said. “I get why anyone wouldn’t want to be in that environment because it’s toxic.”

The Lakers enter Christmas at 19-14, outpacing preseason expectations even though they trail the 23-11 Warriors by 3.5 games. There’s still plenty of work to be done but, like their neighbors to the north, they possess an ambitious ownership group, a savvy front office and a forward-thinking coaching staff. Lakers General Manager Rob Pelinka, like Warriors GM Bob Myers, is a former agent with years of experience around superstars. And Lakers Coach Luke Walton has borrowed from his time as a Kerr assistant by installing an up-tempo, Warriors-like style.

This week’s events indicate that James is already thinking about the next round in the ongoing arms race. The four-time MVP lavished media praise on Anthony Davis and then reportedly treated the New Orleans Pelicans forward to a postgame dinner in L.A. on Friday. Small-market executives cried foul at James’s unsubtle tactics toward the 2020 free agent, a sure sign that the Lakers are officially back on the right track.

The Christmas date between the Lakers and Warriors promises to be a treat, as the back-to-back champs always bring out the best in James, like his memorable 51-point explosion last June. Yes, Tuesday’s contest is a rematch, but it could also be a savvy bit of forecasting by the league office.

Imagine if James’s Lakers were to trade for Davis, or if the Warriors were to lose Durant in free agency next summer. This seesawing pair of franchises — always passing quietly — would instantly be competing for conference supremacy, all these decades later.

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