Mario Andretti Roberts was the starting quarterback for the Dunbar High junior varsity football team in Washington last October when he threw a pass that was intercepted. As Mario made the tackle, his opponent's helmet hit him under the chin.

In a painful split second, Mario, who is 16, suffered a broken neck. When he regained consciousness, he asked a doctor about the numbness in his arms and legs. Tears welled in the physician's eyes, and he could not answer.

Mario was paralyzed.

"I was really shook up -- real depressed," Mario recalled from his bed at the National Rehabilitation Hospital yesterday.

"I kept thinking if only I could go back to that minute, if I could have tackled him a different way, if I should have tackled him at all. Then I started to think that maybe God was punishing me for something I had done wrong," he said.

But those were thoughts from the past, and these days Mario has set his sights firmly in the future again. Although still paralyzed from his chest to his feet, his progress has been so good that doctors expect him to resume his education in September.

"He's bright, very sociable and has a good sense of humor," said Brenda Wilson, a hospital social work coordinator.

"All of those things combined can really help pull a person together."

Seven months ago, Mario thought he was going to spend the rest of his life as a "vegetable."

He became so depressed, he said, that he contemplated suicide. For a youngster on the verge of manhood one second and disabled the next, this was understandable.

But it was not acceptable -- and his family and hospital officials would have none of that.

"What they made me realize is that you can do a lot more than you think if you really try," Mario said, demonstrating his latest accomplishment by raising his arms over his head then returning them to his side. "It may not seem like much. But for me, the more I accomplish, the more I want to try."

There is no way to overestimate the effort that goes into Mario's rehabilitation.

To watch the young man trying to turn from his back onto his side, gasping for breath as he compensates for lungs that hold only 40 percent of the air they used to, fighting back chronic pain in the pit of his stomach, gritting his teeth and pressing for remnants of life in numbed nerve endings, then turning -- through sheer force of will -- onto his side and smiling with delight, is to witness the power of his mind over matter.

Tomorrow, Mario's routine of therapy and television will be pleasantly interrupted when First Lady Nancy Reagan visits the hospital, which is dedicating the neuroscience wing in the name of her stepfather, Loyal Davis, who was a neurosurgeon in Chicago.

It's not that Mario is starved for visitors. His parents and classmates from Dunbar High School frequently come by. And earlier in the year, he received visits from past and present Redskins John Riggins, Sonny Jurgensen and Curtis Jordan.

But Nancy Reagan . . . . Well, that's special. As Mario continues to recover, he has begun to think not just about his own life but also about the lives of the many disabled people who come and go around him.

The stories they tell about the way America treats those who are physically different are as disturbing as whatever health problem they may have.

Of particular concern to Mario is the fact that there has been a startling increase in the number of injuries in school sports, especially head and spinal injuries that could have been prevented.

"I think Mrs. Reagan could bring some of these things to the attention of the public," Mario said.

"The more people become aware that we are people too -- that our bodies may not function like others but that our minds do -- then that would help a lot of disabled people improve."

But with a hearty smile he adds, "I'm not going to kid you: I would just be thrilled to meet the lady."

And if, by chance, he does, the meeting will most certainly be as much of a treat for her as him.