MARTINSVILLE — Calling his elder son “my hero,” NFL Hall of Fame Coach Joe Gibbs told reporters Sunday that doctors had no clear answer for what has caused the brain-function problems that J.D. Gibbs, 46, now confronts.

“Basically, his situation medically – there’s very few answers,” said Gibbs, 74, addressing the media at Martinsville Speedway about three hours prior to the start of Sunday’s STP 500.  “We’ve been dealing with this for about six months, and basically what the doctors say is that they really don’t know.”

Joe Gibbs Racing, the NASCAR team that the former Redskins coach started in 1991 as a competitive outlet after life in the NFL, announced on Wednesday that J.D. Gibbs was undergoing treatment for “symptoms impacting areas of brain function.” The statement went on to say that doctors surmised his health challenge was related to head injury suffered earlier in life.

Speaking publicly for the first time since that announcement, Joe Gibbs recounted the very active lifestyle that his elder son has led, which includes racing motorbikes as a child, playing high school and college football (William & Mary), snowboarding and a brief career as a stock-car racer.

“He loved all those things,” Gibbs said. “We can’t point to any one serious thing that happened to him. Certainly any injury is a possibility that led us into some of the symptoms that he’s experiencing now.”

The somber NFL Hall of Fame Coach spoke for roughly five minutes, his eyes downcast much of the time, and took no questions from reporters. But he interrupted what appeared to be prepared notes several times to thank NASCAR fans and the media for their support over the years.

Gibbs recalled how powerful that support was after one of J.D.’s four children, Taylor, was diagnosed with leukemia at age 2 — and how strong J.D. had been throughout Taylor’s fight. Taylor Gibbs is now cancer-free.

“I think J.D. gains his strength from the fact that he has a personal relationship with the Lord,” Gibbs said, “and I have to tell you that he’s my hero. I kind of watch him, and I don’t know if anybody has ever dealt with anything as courageous as J.D. does.”

Gibbs didn’t reveal a diagnosis for J.D.’s illness, which presented itself with occasional speech problems and cognitive difficulty. But he said he was undergoing treatment and, as a result, would not be at the NASCAR track as often as he typically is.

J.D. Gibbs serves as President of Joe Gibbs Racing, which fields four Sprint Cup teams, three Xfinity Racing series teams and funds the developmental of a handful of young race-car drivers. Gibbs younger son, Coy, 24, runs the family’s AMA Motocross operation and is excpected to take on an increased role in the stock-car operation.