PHILADELPHIA — The Nets wanted to throw the seedings out the window in their first-round matchup against the 76ers, but Philadelphia showed Saturday why they are considered Eastern Conference contenders and the Nets distinct underdogs — even if head coach Jacque Vaughn refuses to use the word.

After a first half in which the Nets hung tough, thanks largely to the play of Mikal Bridges, the quality of the third-seeded 76ers’ roster took over as the game wore on in a 121-101 win in Game 1 of the first round of the playoffs at Wells Fargo Center.

Even with the sixth-seeded Nets red-hot from the floor, they couldn’t match Joel Embiid and James Harden — despite a game-high 30 points from Bridges, who took just two shots in the second half.

Embiid ended up with 26 points, and Harden had 23 points and 13 assists.

Afterward, the Nets pointed to the shot discrepancy: Philadelphia took 19 more shots than Brooklyn, and offensive rebounding, the Nets finished with five while Philadelphia had 14.

“We’ve got to get more looks,’’ said Vaughn, whose team shot 55.7 percent from the field. “I don’t think we had enough 3s. It’s all gonna come down to us rebounding. It’s gonna take that kind of effort.”

What was a six-point deficit late in the second quarter grew nine by the half, and the Sixers pulled away in the fourth quarter.

After winning all four meetings between the two teams this season, the 76ers showed again why they are expected to have little trouble with the Nets — who played well after the departures of superstars Kevin Durant and Kyrie Irving, but are now without any All-Stars.

The 76ers proved to be too much in the end, as they opened up a 20-point lead early in the fourth quarter.

The Nets responded with three straight 3-pointers to close to within 11 with 6:50 to go, but that was as close as they got.

Game 2 is in Philadelphia on Monday night.

“I don’t think our guys were nervous at all,’’ Vaughn said. “They showed me over the course of the game we belong here. That part of it was really good.”

What was less than ideal was the fact the Nets continued to give Philadelphia second chances, as the Sixers finished with 14 offensive rebounds.

Their attempts at double-teaming Embiid were more successful in the first half before Philadelphia and head coach Doc Rivers adjusted at halftime, and Embiid did a solid job of passing out of them.

Bridges credited Embiid and the Sixers for playing Embiid higher in the second half, though Vaughn made it clear he thought the MVP candidate got some help from the officials.

“I hope they’ll be calling traveling and 3-seconds [violations] on the big fella next game,’’ Vaughn said. “I look forward to that.’’

Harden, as well as Tobias Harris (21 points), also made the Nets pay.

“I think we’ve just got to be better and get those 50-50 balls,’’ Bridges said. “We have to rebound, and we can’t turn the ball over.”

But Harden and Embiid also showed why they are among the best in the game, and even when Brooklyn defended well, it ended in points for the 76ers.

“Honestly, some of the stuff they did, we were willing to live with,” Seth Curry said.

Though for a while Saturday Vaughn’s hope that his team might “be very scrappy [and] gritty and turn this game more up and down” nearly worked.

“In playoff basketball, you’re gonna receive some punches and give some punches,” Vaughn said before the game. “So our ability to stay poised for the entire game [is important]. We need to show some poise, as a group, on the road.”