The Pelicans are already plotting for life without Zion Williamson.

The rookie phenom will miss “a period of weeks to start the regular season” with a right knee injury that is not considered very serious, according to ESPN. That means an ACL tear has been ruled out; the timeline sounds more consistent with a knee sprain.

On Friday morning, Alvin Gentry sounded like a coach who will be without his No. 1 pick for a while – not just for Friday night’s preseason finale against the Knicks. Gentry said he can’t commit to a timetable yet for the 6-foot-7, 285-pound Williamson, whose durability is his biggest concern.

It’s a devastating blow to not just the Pelicans but the NBA, which is dealing with a massive crisis with China that will hurt league revenue. Williamson’s Pelicans are scheduled to make 30 appearances on national television, including Tuesday’s season opener against the defending champion Raptors.

Gentry said he talked to Williamson in the morning and reported the youngster’s spirits were fine.

“He’s not dead, guys,’’ Gentry said after shootaround at the Garden. “He’s a typical 19-year-old kid, he’s upbeat, he has fun and he’s living his dream.

“He’s a solid, solid guy. He’s very mature for a 19-year-old, so we’ll just see what goes on there. If anybody is going to be able to stay attached and he’s a great team guy, so he’s going to be with our team regardless of what the situation is.’’

Gentry said he now believes Williamson tweaked the knee in Sunday’s preseason game in San Antonio, though Gentry didn’t notice anything amiss. The former Duke standout has offered a tantalizing glimpse into what his future could hold, averaging 23.3 points and 6.5 rebounds in 27.3 minutes this preseason.

The time Williamson misses, Gentry believes, won’t hinder his development. J.J. Redick will move into the starting lineup Friday for the Pelicans.

“We have good depth,” Gentry said. “That’s the thing [VP] Dave Griffin has done – from the draft and trades. Just from the free-agent market. … It will be opportunity to play guys and shift guys around and play them in different positions.’’

But injuries are a recurring issue for Williamson. He had suffered a right knee sprain in his one season at Duke. And he was shut down in the Las Vegas summer league due to a sore left knee after playing just nine minutes against the Knicks in his opening game.

“Mentally [he has] to stay strong,’’ Pelicans point guard Jrue Holiday said. “I think that’s the biggest battle. It’s not so much what your body does. His body is strong from build and stature. Your body can bounce back. Mentally is where you have to lock in and be patient.”