As an unmistakable feeling of desperation closed in on the Nets, Coach Steve Nash reached toward the deepest recesses of his bench on Saturday and summoned a former star in twilight. Blake Griffin shed his warm-ups, along with some cobwebs, and reported to the scorer’s table.

Griffin, 33, has a bum ankle and a surgically repaired knee that at a previous stage of his career — back when he was dunking over midsize sedans as one of the faces of the N.B.A. — had a full allotment of cartilage. But he had not caught a whiff of playing time in 21 days, dating to the regular season. Now, with the Nets trailing the Celtics in Game 3 of their first-round playoff series, Nash turned to Blake for something, anything — a spark, a lift, maybe even a miracle.

The Nets were willing to take what they could get, and for a few glorious minutes at Barclays Center, Griffin delivered. He sank a couple of 3-pointers. He grappled for rebounds. He even tried to defend Jayson Tatum as the Celtics hunted for favorable one-on-one matchups against him.

Miracles alone do not win playoff series, much less championships. And while there was a time, not so long ago, when the Nets were celebrated as the latest superteam that seemed bound for great things, they have discovered the hard way that titles cannot be store-bought or hastily cobbled together after months of injuries and dysfunction.

“I just felt like we didn’t have the right spirit throughout the entire game,” Griffin said after the Nets’ 109-103 loss, which pushed them to the brink of an early off-season.

Boston, a team that has been ascendant under Ime Udoka, its first-year coach, can close out the Nets with a series sweep on Monday night, and it is likely only a matter of time before this one gets wrapped up regardless: No team in N.B.A. history has come back from a three-games-to-none series deficit.

Aside from that inconvenient truth, the Nets appear acutely aware that the Celtics are a more complete, cohesive team. Just listen to them. Griffin cited the Celtics’ top-ranked defense. (“This is a great defensive team,” he said.) Kevin Durant cited their length. (“I just think they got more size than us,” he said.) And Nash cited their ability to drive to the basket. (“We haven’t been able to contain the basketball,” he said.) This is not a winning formula for the Nets.

On Saturday, the Nets offered up plenty of small moments that typified larger problems. But consider one of their final possessions, as Durant dribbled against the Celtics’ Grant Williams with the hope of creating some space. Finding none, Durant threw a bounce pass to Kyrie Irving that was intercepted by Tatum, who raced away for a dunk that punctuated the win. It was the Nets’ 21st and final turnover of the game.

“Poor decision-making,” Nash said. “Not connecting simple passes, and they’re going the other way.”

The Celtics have smothered Durant, limiting him to 22 points a game on 36.5 percent shooting. On Saturday, he tried just 11 field goals. His postgame news conference sounded vaguely like therapy.

“I’ve just been thinking too much, to be honest, this whole series,” he said.

After shooting 4 of 17 from the field in Game 2, Durant had come into Game 3 wanting to find his teammates more often and “let the ball find me” within the flow of the offense, he said. But he was already questioning himself as he scrutinized another miserable box score in a series full of them.

“I probably should’ve took more shots,” he said, adding: “In my mind, I’m just trying to see how I can help everybody. Sometimes, I end up taking myself out of the game.”

Durant was not the only star who struggled. Irving shot 6 of 17 from the field and missed all seven of his 3-point attempts. Nash blamed fatigue for part of their woes. Irving is fasting for Ramadan. Durant has been supplying huge minutes for weeks — first when the Nets were scrambling to secure a spot in the postseason, and now as they try to survive against a superior opponent.

“They’ve both got to be tired,” Nash said. “Fasting can’t be easy, you know? If I go play tennis and I haven’t eaten, I feel like I’m going to fall over. So I can’t imagine how he feels in an N.B.A. playoff game.”

At the same time, the series has offered contrasting approaches to team building. The Celtics’ core is largely made up of players whom they drafted and developed, a list highlighted by Tatum and Jaylen Brown. That list also includes Marcus Smart, the N.B.A.’s defensive player of the year, and Robert Williams, the fourth-year center who returned to the rotation on Saturday about three weeks after knee surgery.

In that way, the Celtics are reminiscent of contenders like the Golden State Warriors and the Memphis Grizzlies, teams that developed continuity and chemistry by sticking with their young players.

The Nets went the other way, acquiring high-priced stars like Durant and Irving while trading away their draft picks and prospects. It was championship or bust from the start. Sometimes that experiment pans out. The Los Angeles Lakers, after all, won the championship in 2020 by following a similar script. But that seems to be the exception these days, and the Lakers have since crumbled into a pile of very expensive and aging dust after mortgaging their future to try to win now. The Nets may not be far behind.

The Nets, of course, have had a particularly disjointed season, and even before the start of Game 3, Nash was rattling off an abridged list of the challenges his team had faced: not having Irving for much of the season because he refused to be vaccinated; trading James Harden to the Philadelphia 76ers; losing Durant for six weeks because of a sprained ligament in his knee. Nash said he was not making excuses, but …

“We’ve had very few pockets with everyone able to play,” he said.

At this point, they may have only one of them left.