The Indiana Pacers pushed the top-seeded Boston Celtics to the brink of elimination Friday night with a 112-104 win at Gainbridge Fieldhouse, taking a 3-1 lead in the series and sending the bracket into a weekend in which as many as four first-round matchups could be forced to a deciding Game 7. The result, on a night when the Los Angeles Lakers also dropped Game 5 in Phoenix and the Cleveland Cavaliers fell behind the Orlando Magic for the first time, has left league executives bracing for a postseason calendar that may extend the conference semifinals into the second week of May.

Tyrese Haliburton scored 31 points and handed out 14 assists for Indiana, his third straight game with at least 30 and 10. Boston, playing without forward Jaylen Brown for a second consecutive game after a right hamstring re-aggravation in Game 3, was led by 33 points from Jayson Tatum and 21 from Derrick White but shot 8 of 33 from beyond the arc and committed 16 turnovers. The Pacers, who closed the third quarter on a 19-4 run, never trailed in the second half.

“This is the position we wanted to put ourselves in, and now we have to finish it,” Pacers head coach Rick Carlisle told reporters in Indianapolis after the game. “Boston is going to play their best basketball of the series on Sunday. We expect that, and we have to play ours.”

Brown’s status for Sunday’s Game 5 at TD Garden remained uncertain Friday night. Celtics head coach Joe Mazzulla, asked whether his All-Star forward had a realistic chance to return, said only that Brown would be re-evaluated Saturday morning. The Celtics, who finished the regular season 62-20 and had been installed as championship favorites by most sportsbooks as recently as a week ago, have now lost three straight playoff games for the first time since the 2018 conference semifinals.

In Phoenix, the Suns took control of their series with the Lakers behind 38 points from Devin Booker, who returned from a one-game absence with a left calf strain and played 39 minutes. The 114-108 win gave Phoenix a 3-2 series lead and put the Lakers, who stunned Denver in Game 1 of their first-round series before Memphis upset that bracket entirely, one loss from elimination. LeBron James, in what he confirmed earlier this month would be his final NBA season, scored 28 points and added 11 assists; head coach JJ Redick, asked afterward whether he had considered changing his rotation for Sunday’s Game 6 at Crypto.com Arena, said the Lakers would “play the same five-out group that got us here, with the same minutes pattern.”

The night’s other completed game was in Orlando, where the Magic took a 3-2 lead over the No. 2 Cavaliers with a 96-89 win at Kia Center. Paolo Banchero, returning from the right ankle sprain that cost him most of March, scored 27 points on 10-of-19 shooting and grabbed 12 rebounds. Donovan Mitchell led Cleveland with 30 points but shot 1 of 9 in the fourth quarter; head coach Kenny Atkinson said his team’s late-game offense had become “predictable in ways we can fix between now and Sunday.”

The Cavaliers’ wobble is the second East top-three seed to slide toward an opening-round exit, after Miami’s 4-0 sweep of the No. 2 New York Knicks earlier in the week. Heat forward Jimmy Butler, who has not played since closing out that series Tuesday, told reporters in Miami on Friday that he would be ready for the conference semifinals “whenever they ask.”

Only one series in either conference has been decided in straightforward fashion. The Oklahoma City Thunder closed out the Sacramento Kings in a four-game sweep Thursday, advancing behind a 41-point performance from Shai Gilgeous-Alexander, who has averaged 34.5 points on 55 percent shooting across the round.

Elsewhere out West, the Memphis Grizzlies and Denver Nuggets are tied 2-2 in a series that has been defined by the absence of Nikola Jokic, sidelined since Game 2 with a left wrist sprain. Nuggets head coach Michael Malone said Friday that Jokic had progressed to “live shooting” but had not been cleared for contact; Game 5 in Denver is scheduled for Saturday night. The Minnesota Timberwolves, the West’s No. 6 seed, took a 3-1 lead over the No. 4 Los Angeles Clippers earlier in the week and can clinch with a road win Saturday afternoon at Intuit Dome. Houston leads Golden State 3-2 after a Friday-afternoon win at Toyota Center in which guard Jalen Green scored 35.

“Even people inside the league are having trouble keeping the bracket straight in their heads,” said Karen Maldonado, a sports-media analyst at MoffettNathanson. “When you have this many top seeds on the wrong side of a series, the conference semifinal seeding scenarios start to matter more than the series themselves, and that’s a problem the league is going to have to think about.”

Saturday’s slate includes Game 5 in Denver, a potential clincher for Minnesota in Los Angeles, Game 5 in Houston between the Rockets and Warriors, and Bucks-Hawks Game 5 in Milwaukee, with Atlanta leading 3-1 after Giannis Antetokounmpo’s back soreness limited him to 24 minutes Thursday. Sunday’s headline games are Pacers-Celtics in Boston and Lakers-Suns in Los Angeles, both of which could end first-round series that began only a week ago.

Major League Baseball, entering its fifth week, provided a quieter counter-rhythm to the basketball noise. The Detroit Tigers and Baltimore Orioles remained tied atop the American League at 16-6 each; the New York Yankees, 8-13 and last in the AL East, placed veteran starter Carlos Rodon on the 15-day injured list Friday with what the club described as left forearm fatigue. The Los Angeles Dodgers, 15-7 and leading the National League West by four games, hosted the San Francisco Giants at Dodger Stadium.

NBA Commissioner Adam Silver, in a brief statement issued through the league office Friday evening, said the conference semifinal bracket and broadcast schedule would be finalized within 24 hours of the last first-round series ending. Privately, league officials told club communications staffs to plan for the second round to open no earlier than Tuesday, May 5.