MIAMI — The 76ers have to be frustrated.

They blew a golden opportunity to clinch the Eastern Conference’s No. 1 seed and garner some rest that comes with it. Now, they’re here in South Florida looking to regain their shooting touch and secure the top seed while facing the Miami Heat.

The first-place Sixers (47-22) will clinch with a victory in their remaining three games or if the Brooklyn Nets and Milwaukee Bucks both lose one of their final three matchups.

But on paper, Thursday night’s game will be the Sixers’ toughest test since facing the Milwaukee Bucks on April 24 at Fiserv Forum.

The Heat (38-31) have won three straight and 10 of their last 13 games. Miami ranks sixth in the league in opponents’ field-goal percentage at 45.7, three spots behind the Sixers (45.2). The Heat are fifth in the league in scoring defense, holding teams to an average of 108.05 points. The Sixers are sixth at 108.1.

So on Thursday, they’ll have face an opponent that’s similar in regards to being dominant defensively.

With that, the Sixers must shoot better than in Tuesday’s 103-94 road loss to the Indiana Pacers, especially if Joel Embiid remains out.

As in Tuesday’s game against the Pacers, Embiid is listed as questionable against the Heat with a non-COVID-19 illness. He did not accompany the Sixers on the trip to Indianapolis.

Without him, Philly shot 29.5% in the second half. The Sixers made just 13 of 44 shots, including going 2-for-14 on three-pointers. Danny Green (0-for-4), Mike Scott (0-for-3), who started in place of Embiid, and Seth Curry (0-for-4) combined to shoot 0-for-11 after intermission. The Sixers were outscored by 52-32 during that time.

“We really didn’t have any execution,” coach Doc Rivers said after Tuesday’s game. “We really didn’t. First half, first quarter, we were brilliant. You know, the first quarter, we were brilliant with moving the ball, getting the ball in the right spots, running our stuff.”

But Rivers thinks the Sixers’ players lost their focus while worrying about the referees’ calls. Ben Simmons was one of those players.

The three-time All-Star point guard finished with 20 points. Fourteen came on 6-for-10 shooting in the first two quarters. At that time, Simmons had only one foul. He had four points in the third quarter on 2-for-4 shooting. But in the fourth quarter, Simmons was called for four fouls. He also lost his offensive aggressiveness, scoring two points on 1-for-2 shooting.

Simmons was asked if he settled on what the Pacers gave him or just tried to get everyone involved in the second half. He responded by talking about the team.

“I think we slowed down our pace,” Simmons said. “I mean, we got a lot of good looks. We just didn’t knock them down.”

Whether it’s being aggressive or making shots, the Sixers must sustain their play in what could be a second-round playoff matchup.

The Heat are fifth in the conference with three games left. If they remain in that spot or move up to fourth, they’ll compete in the four-vs.-five seed opening-round series. The Sixers would face that series’ winner, assuming they get the No.1 seed and win their first-rounder.

In addition to Embiid, Sixers reserve guard Matisse Thybulle (swollen left hand) is questionable. Reserves Shake Milton (right-knee soreness) and Furkan Korkmaz (sprained right ankle) are probable. For Miami, former Sixer Jimmy Butler (eye contusion) is questionable while Victor Oladipo (season-ending right quadriceps surgery) is out.