The Nets have been waiting all season for their Big Three to fire on all cylinders.

With one week to go before the playoffs, they finally are.

The Nets got huge contributions from Deron Williams, Joe Johnson and Brook Lopez, who combined to score 81 points as the Nets knocked off the Pacers, 117-109, in front of a sellout crowd of 18,165 at Bankers Life Fieldhouse.

The win, combined with a loss by the Bulls in Toronto, locked up at least the No. 4 seed and home-court advantage in the first round of the playoffs — and kept alive the slim chances the Nets (47-32) have of passing the Pacers (49-30) for the third seed.

“This is pretty big,” said Johnson, who finished with 24 points on 9-for-17 shooting, including 4-for-8 from 3-point range. “We get to start the postseason off at home, so we have an advantage, but we’re not satisfied.

“Hopefully we can move up even higher, so we’ve still got work left to be done.”

For the second straight game — and fourth time this season — Williams, Johnson and Lopez each finished with more than 20 points, and they wound up needing every one of them in order to hold off the Pacers and complete a 3-0 sweep of their season series.

Williams, in particular, was sensational, finishing with 33 points and 14 assists, including a blistering second quarter in which he scored 20 points on 7-for-12 shooting (4-for-7 from behind the 3-point arc).

“I just got free a couple times, hit a couple baskets and started feeling it,” Williams said.

But after Williams and Brook Lopez, who finished with 24 points — including 16 in the first half — helped the Nets build a 69-50 halftime lead that grew to 24 points early in the third quarter, the Pacers stormed back and closed the third with a 33-16 run to get within 92-85 going into the fourth.

The Nets had issues with the way the game was officiated in the third quarter. Reggie Evans, who had already picked up a technical foul in the first half, was ejected after getting a second when, after picking up his fourth personal foul in the third quarter, he fired his headband at the Nets bench as he walked off the floor.