The Nets made the biggest splash. Philadelphia may have the last laugh.

Though Brooklyn stole Sunday’s spotlight by landing Kevin Durant and Kyrie Irving at the opening of free agency, the 76ers ended the night looking like the East’s best team — having retained Tobias Harris (five years, $180 million), stolen Al Horford (four years, $109 million) from rival Boston and acquired solid wing Josh Richardson in a sign-and-trade with Miami for Jimmy Butler.

Strengthening the Joel Embiid/Ben Simmons-led core, which was ousted from the playoffs in the conference semifinals on a Game 7 buzzer-beater by the eventual-champion Raptors, Philadelphia made its first big move by offering the fifth-largest contract in total value in league history to Harris — who turns 27 in two weeks, and averaged 18.2 points and 7.9 rebounds in 27 games with the 76ers last season.

Perhaps the more important move came when Horford, a five-time All-Star, spurned a reportedly lesser offer from the Celtics, giving Philadelphia a respected veteran who has made the playoffs in each of his 12 seasons.

Though Butler opted to join the Heat — receiving a four-year, $142 million contract — general manager Elton Brand received Richardson in return, a 25-year-old who averaged 16.6 points last season.

Golden State refused to surrender its dynasty, agreeing to a five-year, $190 million deal to keep Klay Thompson, though he will miss most, if not all, of next season after tearing his ACL in the NBA Finals.

Philadelphia was one of five teams (along with the Nets, Celtics, Bucks and Mavericks) to dole out the largest contract in franchise history, accounting for much of the roughly $2 billion spent on the first night of the negotiating period for the most anticipated free-agent crop since the 2010 class led by LeBron James.

Reigning NBA Finals MVP Kawhi Leonard and DeMarcus Cousins remain available, among others. Players cannot officially sign contracts until July 6.

Like the Nets, Dallas wouldn’t let a devastating injury stop it from making a franchise-altering move. While the Knicks were left sitting on a mountain of money, their former franchise player, Kristaps Porzingis, cashed in with a five-year, $158 million deal from the Mavericks, who acquired him in January. The 7-foot-3 forward hasn’t played since tearing his ACL in February 2018, but only turns 24 this summer. He averaged 22.7 points, 6.6 rebounds and 2.4 blocks during his third season with the Knicks.

The Celtics ensured they’ll remain in contention after losing Irving and arguably upgraded their backcourt — and chemistry — by bringing in Kemba Walker with a four-year, $141 million contract. The 29-year-old, three-time All-Star had spent his entire career in Charlotte, but he’d missed the playoffs in three straight years and was moved in a sign-and-trade — which brought back Terry Rozier to the Hornets on a three-year, $58 million deal.

Milwaukee made sure MVP Giannis Antetokounmpo could make another title run, signing Khris Middleton to a five-year, $178 million contract while also bringing back center Brook Lopez on a four-year, $52 million deal. Middleton, a former second-round pick who will turn 28 this summer, made his first All-Star Game last season and averaged 18.3 points, 6.0 rebounds and 4.3 assists.

Milwaukee was only willing to spend so much, though, sacrificing 2017 Rookie of the Year Malcolm Brogdon, who was sent to Indiana in a sign-and-trade and rewarded with a four-year, $85 million deal. The Bucks received a first-round pick and two future second-round picks from the Pacers.

The Trail Blazers eliminated any potential anxiety two years down the road by signing four-time All-Star Damian Lillard to a four-year, $196 million extension, following the team’s first conference finals appearance in 19 years.

Less-heralded, though no less staggering, deals were littered throughout the league.

Orlando retained Nikola Vucevic with a four-year, $100 million deal, then lured Terrence Ross with a four-year, $54 million contract. Sacramento gave a four-year, $85 million deal to Harrison Barnes. Utah handed a four-year, $73 million contract to Bojan Bogdanovic. Ricky Rubio received a three-year, $51 million pact from Phoenix. Jonas Valanciunas will sign a three-year, $45 million contract with Memphis. Thaddeus Young will get a three-year, $41 million deal from Chicago.

The surprises have only started.