SAN FRANCISCO — The two biggest titans of the NBA’s 21st Century are meeting for the fourth time on Christmas Day.

Given the point each of them are in their careers, it could be one of, if not the last, time Steph Curry and LeBron James match up on the NBA’s signature regular season day.

But until they retire, whenever that may be, they’re still the main attractions.

“The same way that Magic and Larry in the 80s, MJ in the 90s, Kobe for a long time, (in some ways) they’ve carried the league,” Lakers head coach JJ Redick said.

“Popularity, growth, all that stuff. They’ve had a big part in that. Certainly those consecutive Finals against each other really helped in that. I think overall, they’re different careers, different legacies, but to me, those guys — both of them — have a strong case if you want to have Mt. Rushmore of the greatest four NBA players of all time.”

James turns 40 at the end of the month. Curry turns 37 in March. They’re each still capable of taking over games and rate very highly in advanced metrics like value over replacement player and box plus/minus.

But they’ve also shown signs of decline. It would be truly unbelievable if they didn’t.

In the past week, Curry had two of his worst games of his career — a two-point dud against Memphis and a 2-for-13 night versus Indiana. He hasn’t had as much success shedding face-guards and double teams and appears less inclined to drive to the basket at times.

Asked by ESPN’s Malika Andrews if he thinks about how much longer he wants to play, Curry said “more than I probably have before.”

“It’s okay to accept and acknowledge that the end is near at whatever point,” Curry said. “But only because it allows you to enjoy what is happening right now. The more you talk about it, the more you acknowledge it, it levels up the sense of urgency of the moment now.”

James, meanwhile, has scored fewer than 20 points in 11 of his 27 games played. The Lakers are curiously 9.3 points per possession worse with him on the court. Although he has ramped up his defensive intensity to a great degree recently, James isn’t nearly the dominant defender he used to be. Earlier this year, he left the team for eight days for a physical and mental refresh.

“Part of it is just Father Time,” Warriors head coach Steve Kerr said. “If you’re 40 or almost 37 in Steph’s case, it’s a lot harder — physically and emotionally —  to face what those guys face night after night after night. There’s a reason players have to retire. They can’t do it forever.”

Both the Warriors and Lakers have struggled, floating to the thick of the Western Conference play-in picture. They each probably need a major trade to vault back into the type of postseason relevance Curry and James are accustomed to.

They’re still the league’s biggest draws. Either Curry or James has led the NBA in jersey sales every year since the 2013-14 season. Nationally televised games featuring either of them typically rate better. Curry and James have combined for 30 All-Star selections, eight championships and six MVP awards. Their legacies are signed, sealed and delivered even independent of the final chapters they write.

Even as their personal rivalry came to a head with four straight Finals meetings from 2015 to 2018, Curry and James have always had mutual respect for each other. They teamed up for the first time this summer, when they led Team USA to Olympic gold in France. Coaching them was one of the greatest thrills of Kerr’s coaching career.

On Wednesday, when James emerged from the visiting tunnel for warmups, he playfully tried to block a Curry practice shot before the two embraced with a bear hug.

If it’s their last Christmas sharing a court together, they’ll go out with a wham.