76ers center Joel Embiid may not be available to play at the start of the NBA season after the latest setback in the healing of his right foot, an NBA source said Sunday. There's also a legitimate chance that the 7-footer could miss the entire season.

Another source, an Eastern Conference executive, said Sunday that the 76ers' rebuilding plan is doomed if Embiid is unable to remain healthy or play at a high level.

"He was their guy," said the executive, who spoke on condition of anonymity. "They were hoping he was a franchise player. If he's not a franchise player, their whole plan is gone. . . . If Embiid can't play or if he can't reach a superstar level, their plan is really in trouble."

The team announced Saturday night that Embiid has had a setback in his recuperation. The first-round pick from Kansas missed what would have been his rookie season after undergoing surgery last June to repair a stress fracture in the navicular bone in his right foot.

The Sixers had no public statement on Sunday. General manager Sam Hinkie said in a statement Saturday that a recent CT scan, performed in Los Angeles, revealed less healing than anticipated at this point. His recovery time was expected to be five to eight months. But the Sixers handled his rehabilitation with caution and he was expected to sit out the season.

"Our priority remains providing Joel with every opportunity to ensure he has a long and successful NBA career," Hinkie said Saturday. ". . . We will continue to consult with the experienced team of doctors who have been an integral part of his evaluation, while also engaging in dialogue with a broader set of experts and specialists."

It was unknown Sunday if Embiid, 21, would have to undergo another surgery that could sideline him for part of the next season. The team was still gathering information and nothing had been ruled out.

The Cameroonian big man is not expected to participate in the two NBA summer leagues the Sixers will play in next month. It is not known how long he will be sidelined.

"Whatever it is, I doubt you are going to see him play at the start of the season," the NBA source said, pointing out that he expects the Sixers to use even more caution in dealing with Embiid's latest comeback.

Embiid has yet to participate in five-on-five scrimmages with the team. Hinkie said last June that the time line for the center's return was five to eight months, meaning he was scheduled to be able to play by February.

Some sources have said the delay was the result of the foot's not healing properly and Embiid's lackluster work ethic. Those sources said the Sixers did not fully disclose the severity of the injury. The Sixers had said publicly that Embiid's healing process was on schedule before their news release Saturday.

And as they were last season, the Sixers are prepared to keep Embiid out as long as possible in order to focus on his long-term health. As a result, there's a possibility that he could miss another entire season.

"I don't think anyone [around the league] is surprised at all," the NBA executive said. "Cleveland and Milwaukee [which picked first and second in last summer's draft] would not consider him because of the foot and back injuries."

There's a chance this injury could hinder Embiid's career the way it has for other 7-footers. Like Embiid, Yao Ming suffered a stress fracture in the navicular bone in 2008 and again in 2009. That injury forced Yao to retire in 2011.

A stress fracture in Embiid's lower back kept him out of the Big Twelve and NCAA tournaments during his lone season at Kansas in 2013-14. Embiid initially hurt his back Feb. 8 against West Virginia. After returning to action, he aggravated the injury March 1 at Oklahoma State.

Another league source said Embiid's latest setback would not influence the Sixers' plan in the June 25 draft. He said the team still would use the third overall pick on the best available player regardless of position.