The 76ers have been mostly unsuccessful in trying to pair 6-foot-11 post players Jahlil Okafor and Nerlens Noel on the court. In the long run, one of them might have to go, an NBA executive said Monday.

"Everything will come down to Joel Embiid. That's the big question," said the executive, who asked not to be identified. Embiid has been sidelined for the second consecutive season after foot surgery.

"If Embiid can play, then in my opinion, they will have to trade Okafor, because Embiid and Okafor cannot play together," he added. "If Embiid can't play, then they have to decide whether to keep both Noel and Okafor. But the combination hasn't worked out.

"Or they can trade one of the two and see if they can get strength at another position because, basically right now, they have three centers."

Okafor was selected third overall out of Duke in the 2015 NBA draft. He leads all rookies in scoring at 17.4 points per game. He also ranks third in rebounding at 7.5 per game. Okafor, 20, is perhaps the NBA's most skilled rookie big man since the San Antonio Spurs drafted Tim Duncan first overall in 1997.

Noel is a rim protector who can run like someone half his size. His off-the-charts athleticism will amaze you. The 21-year-old averages 10.4 points, 8.2 rebounds, 1.4 assists, 1.5 steals, and 1.4 blocks. He was selected sixth overall by the New Orleans Pelicans in the 2013 draft and traded to the Sixers on draft night.

"I think Noel is more of a winning player because he affects the game in a lot of areas, where Okafor really affects the game in one area: scoring," the executive said.

On paper, Embiid is recognized as the best of the three. He has grown two inches to 7-foot-2, possesses the strength to bang on the block and has three-point range.

However, there's a lot of uncertainty surrounding the future of the third overall pick out of Kansas in 2014.

He had bone-graft surgery to repair the navicular bone in his right foot in August. He will miss the entire season. He missed what would have been his rookie season after surgery in June 2014 to repair a stress fracture in the same bone.

Like Okafor and Embiid, Noel has shown he is better suited to play center. And the team has been successful with him at the position. However, the Sixers are committed to starting the two big men together in their normal starting lineup, with Noel moving to power forward.

Noel is the starting center when the Sixers match up with smaller lineups. Jerami Grant is the starting power forward and Okafor is the backup center.

"I don't think Jahlil can chase guys like the Rudy Gays and Kevin Loves," coach Brett Brown said to being asked why Noel, not Okafor, has to slide to power forward. "I don't think he can do it. Nerlens can better do it."

The league executive said Okafor and Embiid cannot play together. "They are both centers," he said. "They both can only guard centers. They can't defend power forwards or stretch fours in this league."

He believes that Noel and Embiid would work because Embiid can stretch the floor. "He can go out to the three-point line and shoot it," he said. "But when Noel and Okafor end up together, both of them cannot go out further than 15 feet. That makes it really difficult on the offensive end of the floor. And also Okafor is a liability on defense."

Retiring No. 4

The Sixers will retire the No. 4 jersey of the late Dolph Schayes during halftime of their home game against the Boston Celtics on Jan. 23. However, Noel will still wear the number in honor of the Hall of Famer.

Schayes' number will be the ninth retired in team history. The others are Allen Iverson (No. 3), Julius Erving (6), Maurice Cheeks (10), Wilt Chamberlain (13), Hal Greer (15), Bobby Jones (24), Billy Cunningham (32), and Charles Barkley (34).

Schayes died of cancer last month at age 87. He played most of his career with the Syracuse Nationals before the team moved to Philadelphia and became the Sixers.