Greg Clark is not alive to celebrate the 25th anniversary of being drafted by the 49ers out of Stanford.

Would he even have done so?

“Yes,” his widow, Carie, said after a thoughtful pause. “I think he would have celebrated.”

Greg Clark loved football, and his family still does despite its ultimate impact on his brain, which wreaked havoc on him after his NFL career ended in 2001.

He was 49 when he died by suicide last July while alone at his family’s Danville home. A self-inflicted gunshot wound shook their peaceful oasis in Mount Diablo’s shadow.

At 6 a.m. the next day, Carie was on the phone, seeking to learn where to donate her late husband’s brain for scientific study — and for answers.

The Clark family, in an exclusive interview with this news organization, is revealing that Boston University researchers found signs of Stage 3 CTE — chronic traumatic encephalopathy — in Clark’s brain.

“He totally was suffering in silence,” Carie said in an emotional interview, alongside Greg’s brother Jon, this week at a Pleasanton cafe.

“He did all the things theytried to offer, and it just wasn’t enough,” Carie added, referring to treatment options through the NFL and its players union. “I didn’t really know a whole lot, because he was hiding it from me.”

“CTE is a progressive disease, and it gets worse as an individual ages,” said Dr. Ann McKee of the Boston University CTE Center. “Even though Greg retired before age 30, the disease continued to progress, and it spread from those lesions, which is very classic for CTE. His disease had spread into the interior of brain, the parts that control learning and memory.”

The Clarks are not speaking out to place blame. They do not want to burn down the sport. Carie insists on keeping the family’s season tickets to see their still-beloved 49ers with sons Jayden, 22, and McKay, 14.

Jayden will graduate later this year from Southern Utah, where he finished his football career as a linebacker last fall, just months after his father’s death.

Greg Clark played nearly 15 years of football. He was a small-college All American at Ricks College in Utah. Bill Walsh recruited him to Stanford, where he played two seasons and earned a degree in psychology.

He was a third-round pick by the 49ers in the 1997 NFL draft.

Clark had some highlights (four touchdowns over four seasons) and some injuries, the last of which required hamstring surgery that sidelined him all of 2001 before his release in February 2002.

Whether or not Clark had a history of concussions, McKay noted that “it’s those mild hits, called sub-concussive hits, that over time trigger CTE.”

Not long before he died, Clark sent emails to friends and doctors seeking help. Carie, his wife of 22 years, learned of this only after his death.

“We knew he had CTE symptoms. I was shaken when they said he had advanced Stage 3 CTE,” she said.

Greg Clark’s anxiety in 2014 had him seek help. But the medication prescribed to him only put him in a darker place. So, for eight years, he took the homeopathic route with vitamins.

Her husband did not opt into the NFL’s concussion settlement until 2017. Once he joined, he went to Southern California for testing and received free therapy sessions.

He didn’t lead a path of destruction. His marriage and finances were intact. He and Jon were business partners in East Bay real estate for 14 years, and Greg built a complex portfolio through it.

“Greg was highly intelligent, and he was trying to find ways to make himself better,” Jon recalled. “The last few years of his life ... talk about carpe diem.”

If a “powder alert” hit his brother’s phone regarding snowfall, he’d head out to ski. He’d enthusiastically hit secret fishing holes or spontaneously join his brother to hike Half Dome.

“He was a genuine person,” Brent Jones, the former 49ers tight end, said at Clark’s memorial service. “You’ve heard so many stories today about Greg and his character traits and how he could sometimes have a hard-edged exterior, until Carie came along, fortunately. But he was soft inside and had such a great heart.”

But stressful business in January 2021 brought on more anxiety. Then came a mountain bike accident and a poison oak breakout that put him on medication, on top of other medication he was taking.

“A six-week spiral” ensued, according to Jon, one of Greg’s six younger brothers and his business partner for the past 16 years.

Clues at Clark’s deteriorating state were irritability, emotional distance, memory lapses, isolation, anxiety and depression, and his prescribed medicine for the latter is what McKee called “the final straw.”

The Boston University CTE Center has nearly 1,300 brains it has researched, including those of close to 800 football players and over 300 who played in the NFL.

“It’s not unique anymore,” McKee said of CTE diagnoses. “It’s unfortunate, it’s depressing, and it’s tragic every single time.”

Greg Clark was aware of the CTE findings in fallen NFL players who died by suicide, and he shared his disbelief each time with his wife. Those deaths included Dave Duerson (2011) and Junior Seau (2012), as well as infamous cases involving convicted murderer Aaron Hernandez (2017) and Philip Adams (2021), who killed himself after shooting six people to death in South Carolina.

“A lot of these guys, it’s not obvious they’re suffering from a brain injury,” McKee said. “They look fine. They for the most part get through the day without difficulty. It’s the subtle changes.”

Dr. Allen Sills, the NFL’s chief medical officer, said the diagnosis “underscores the urgent need for continued rigorous scientific research related to the prevention, diagnosis and treatment” of traumatic brain injury, concussion and CTE.

CTE can be confirmed only posthumously. Nine months after Clark’s death, his family gathered for a videoconference with McKee. Clark not only had CTE but a severe case.

The diagnosis hit Jon “like a punch to the gut. It’s just a feeling of sorrow of what he was dealing with — alone.”

Clark was “a little early” to reach Stage 3 CTE, which typically hits around age 56. But Carie said it provided a “weird sense of relief.

“Suicide has such a stigma. It was confirmation he wasn’t well. He was not Greg. ... I can look at my boys and say, ‘Your dad was really, really ill.’

“Some peace comes from that,” she added. “But the pain and reality will never go away.”

The National Suicide Prevention Hotline is at 800-273-8255.