NEW ORLEANS — In the months before the rookie phenom Zion Williamson made his belated and stirring N.B.A. debut on Wednesday at age 19, he spent his rehab from knee surgery as a 6-foot-6, 284-pound gymnast learning to stick the landing.

With guidance from the medical staff of the New Orleans Pelicans, Williamson tried to correct biomechanical flaws suspected of contributing to a tear in the lateral meniscus — a rubbery, shock-absorbing cartilage on the outside of his right knee.

The meniscus was trimmed during surgery in October. Then, said Williamson, who can leap so much higher and is so much more agile than one might expect of someone his size, it was time to learn how to run and jump more safely. Williamson trained himself to land with his knees bent, instead of straight-legged. The bent-knee landing helps disperse the pounding forces of basketball. He also worked to avoid tilting his knees inward when landing with a rebound or making a sharp cut, which can put added stress on the outside of the joints.

In his first official game, Williamson scored 22 points in a loss to San Antonio, including 17 in a breathtaking flurry over three minutes of the fourth quarter. Still, he has missed half of his rookie season. And while his nascent professional career is full of luminous and generational possibility, it is also emblematic of growing worry among N.B.A. officials about young players who have played basketball almost exclusively as teenagers and then enter the league more vulnerable to injury than they should be.