It is a tale of two returns.

Kyrie Irving is back with the Nets — well, on a part-time basis at least — after spending the season sidelined for reasons of his own making: the stubborn refusal of a Covid-19 vaccination.

Klay Thompson will soon suit up for the Golden State Warriors after 30 months in which unlikely injuries pried him away from basketball. Thirty months, two and a half seasons, of hard and sometimes heartbreaking rehab.

Thompson’s comeback brings us the opportunity to marvel again at one of the most symbiotic connections in sports. From 2012 until his initial injury in 2019, Thompson and Stephen Curry, his close friend and backcourt mate, offered steady lessons in combined greatness: ballet-like cutting and passing, orbital jumpers from every angle — all of it performed in remarkable tandem.

We finally get to see Klay and Steph, Part II.

Thompson’s return does bring about questions, but they are as simple and straightforward as his pull-up 3-pointers. Will he return to the All-Star form that helped lead Golden State to three N.B.A. titles? And if so, how long will it take?

Irving’s comeback is another matter altogether. His return is a gamble. First, it sends a dubious message about personal responsibility during a public crisis. It also leaves the Nets in a muddle. The team is close to realizing its significant dreams, even as it now operates under the shadow of Irving’s most recent act: Here one game, gone the next.

Few in basketball have ever been as elusive as Irving is when he winds through opposing teams and slices down the court — a fact underscored by Irving’s return to the Nets on Wednesday, when he scored 22 points and helped lead the team back from a 19-point deficit to defeat the Indiana Pacers, 129-121.

Irving is just as hard to pin down off the hardwood. There may not be an N.B.A. point guard as fine at getting his teammates involved with pinpoint passing. But he also has a reputation for a history of being an erratic personality who can just as easily implode teams. (See: Boston Celtics; Cleveland Cavaliers.)

Irving’s belief that the earth is flat? That was once a funny sideshow that he couldn’t quite explain in any manner that made sense.

His refusal to be vaccinated during a pandemic that has killed at least 5 million worldwide and more than 830,000 Americans, with many of the hardest-hit communities being the Black and Brown neighborhoods that Irving takes pride in helping? That’s a perplexing travesty.

What a difference three months makes in this troubled world. In October, Nets officials were adamant they would not allow Irving on their team so long as he refused to abide by New York City mandates requiring workers at venues as large as the Barclays Center and Madison Square Garden to inoculate against the virus.

Why bother if Irving could play only when the team was on the road?

“Each member of our organization must pull in the same direction,” General Manager Sean Marks said.

Of course, the Nets waffled. Like almost every team in the N.B.A., they’ve been trotting out patchwork lineups filled with minor-league replacements because Covid-19 protocols have sidelined so many regulars. Never mind that by this week, every player kept from the team because of positive coronavirus tests had returned — the Nets had cover to reverse course on Irving.

Brooklyn made a business decision, altering its stated principles, even as New York City finds itself swamped by another surge fueled by another coronavirus variant in this plague. Irving is back, adding to the bottom line that really matters in sports: winning and the heady financial rewards that come with it.

The Nets, already gifted with Kevin Durant and James Harden, are chasing a championship and Irving’s return brings with him not questions of wonder and potential, but of logistics.

Does Kyrie Irving give the Nets the best chance to win a championship if he can’t play at home, in Manhattan against the crosstown Knicks or in Toronto versus the rival Raptors because vaccination is a requisite for entering Canada?

N.B.A. championship basketball feeds off deep continuity. It requires a roster full of teammates who know one another’s every last on-court tendency. It flows with the timing and rhythm of a great Miles Davis quintet. Are the Nets better for having Irving? Or will toggling him in and out of the lineup through the regular season and into the playoffs keep them from ever getting into that kind of title-winning groove?

We’ve seen no better N.B.A. tandem, no better groove than Curry and Thompson playing off one another before Thompson’s initial injury. Even when the team had Durant, the most potent basketball force on the planet, the two longtime guards were the Warriors’ beating heart. (Aided, we know, by Draymond Green.)

This season, Golden State has been superb, perched again atop the league standings with Curry playing at league M.V.P. level. But nothing will feel quite right until Thompson is back in the mix.

His return could come as soon as Sunday when the Warriors play the Cleveland Cavaliers in San Francisco. That would be 941 days since he tore the anterior cruciate ligament in his left knee during the 2019 N.B.A. finals, and 417 days since he ripped his right Achilles’ tendon while working out.

During that time, the N.B.A. has been bereft of one of its smoothest shooters and best defenders, a player popular enough to leave fans and most of the league mesmerized by even the smallest viral video clips showing him on the mend. There’s Thompson with his bulldog Rocco, cruising in a cool convertible. Or captaining his 37-foot fishing boat on the San Francisco Bay, gushing about the return: “I get chills when I think of coming back, I can’t wait!”

Or practicing with the Warriors’ developmental team, hitting a dart-like 3-point game-winner.

There may be no more touching N.B.A. moment this year than when a sorrowful Thompson remained on the bench in street clothes after a home win against the Portland Trail Blazers, a towel draped over his head as he commiserated on all he was missing.

“Two-plus years is a long time,” Curry said in a November interview, speaking of his backcourt mate’s return. Curry said he’d figured this season would be the hardest part of Thompson’s journey, since he was practicing with the team and oh-so-close to an official return.

“We’re talking weeks instead of months now,” Curry added.

And now we are talking days.

Thompson’s return will spark plenty of examination, but it won’t have to do with whether he has done all he can to protect himself and others from the virus. It will be about basketball. Can he get back to form, and what team in the league can stop the Warriors if he does?

The Warriors’ prime nemesis may well be Brooklyn. To be Golden State’s spoiler, or to win the title from some other Western Conference team, it will need to fire on all cylinders. It will need continuity, timing, and trust that can only come from the Nets’ Big Three playing together full time.

Don’t count on it.