The unlikely phenomenon of DeJuan Blair begins with a checklist of everything that should disqualify him as an effective N.B.A. player.

He is a power forward who is listed at 6 feet 7 inches, but is closer to 6-5.

He is a rebounding specialist who barely leaves the ground.

He has no anterior cruciate ligament. In either knee.

The catalog of justifiable doubts is as thick as Blair’s torso. His playful smile only grows wider at every recited item.

“Yeah,” said Blair, the San Antonio Spurs rookie out of Pittsburgh, drawing out the word and punctuating it with a chuckle. “That’s why it’s so amazing. That’s why it’s so fun.”