Nobody knows exactly how it happened. One moment, he was in a preseason workout with his teammates. The next, he was lying lifeless on the ground.

Doctors saved Nick Knapp’s life that afternoon in 1994. Afterward, medical experts placed a small defibrillator in Knapp’s chest to jump-start the basketball player’s heart if it ever quit on him again. It never did. No one — not the country’s best cardiologists, not the country’s best physiologists and certainly not Knapp himself — could figure out what had happened.

Later that year, the Peoria, Ill., native accepted a scholarship from Northwestern. He had the full support of the coaching staff, thinking that he’d surely be able to play.

But upon arrival in Evanston, NU team physicians Howard Sweeney and Mark Gardner looked at Knapp and at his medical history and ruled him ineligible. Knapp offered to sign any waiver that would free NU of liability were he to collapse again — but it wasn’t enough.

“After I got there, the president and athletic director pulled the rug out from under me and told me I couldn’t play,” Knapp said.

For two years, Knapp lived the life of an NU basketball player without ever actually playing the game: He learned opposing offenses, attended practices and watched games from the sidelines.

For two years, the university fought Knapp in federal and appellate court to keep him and his bum ticker from touching a basketball at NU.

For NU, the risk was simply too great, a lesson the university learned again this summer.

On Aug. 3, Rashidi Wheeler, a senior strong safety on NU’s football team, collapsed and died from an asthma attack during a workout. An early look at the circumstances of his death has led Wheeler’s mother, Linda Will, to file a lawsuit against NU in which she blames her son’s death on a poorly trained and equipped medical staff. The suit names administrators, coaches, trainers and interns — some of whom were not present when Wheeler collapsed.

While it reviews the case, the university has declined to answer any questions concerning Wheeler’s death and the ensuing events.

Wheeler’s death doesn’t change Knapp’s stance. He knows what it’s like to be an athlete, to play for the love of the game. And Knapp knows that Wheeler, or any athlete, shouldn’t play if his life is at risk.

“If he knew there was a problem and he felt he had to be there, then the administration doesn’t have a firm grip on things,” Knapp said. “NU has to ensure that this doesn’t happen again.”

This comes from a player who fought the university tooth and nail for years to loosen such precautions. Knapp knows firsthand that accidents can’t be avoided and that one can’t live life in fear. And sports certainly can’t take place with such caution.

Playing Division I basketball was Knapp’s dream. And while his collapse and the surgery that followed kept him off the court his senior year, he tried to make that dream come true at NU. After accepting an athletic scholarship, he even lent a hand to the coaching staff, helping to draw in one of the program’s strongest recruiting classes, which included Midwest natives Julian Bonner, Sean Hanlon and Matt Moran.

Knapp was a model recruit. At Woodruff High School, he competed against athletes who went on to win state titles and start at Illinois, Indiana and Purdue. The valedictorian in one of the area’s larger high schools, Knapp scored a 32 on his ACT and was looking at Cal and Stanford before NU knocked on his door.

Assoc. Athletic Director Ken Kraft remembered Knapp as a talented student and player. However, Kraft agreed with the university’s decision to keep him from playing.

“He was a highly sought-after player,” Kraft said. “Northwestern felt it was looking out for Knapp’s best interests.”

After filing the lawsuit, Knapp’s case went to federal court, where the judge sided with him, ruling that NU’s actions were illegal under the Federal Rehabilitation Act. NU then brought the case to appellate court, where the ruling was overturned. The case hinged on Knapp’s argument that intercollegiate sports constitute a “major life activity.” The law prohibits federally assisted institutions from discriminating based on disability.

Knapp insists that the perception of sports in the various courts resulted in the different rulings.

“The federal judge that agreed with me played sports in college,” Knapp said. “One of the appellate judges (who sided with NU) said I could find the same camaraderie in the school band.”

After being told he couldn’t play, Knapp packed his bags and transferred to Northeastern Illinois. When the school’s Division I basketball program folded, Knapp transferred to Ashland University, a Division II program in Ohio. He played two years at Ashland, leading the team in three-point shooting both seasons.

“Playing four years of Big Ten basketball was my dream,” Knapp said. “Northwestern was the only school that told me my condition was a problem.”

He earned a master’s degree in educational administration from Ashland and acted as an assistant coach for the basketball team after his eligibility ran out. Currently, Knapp is back in Peoria weighing job offers and talking to teams in England, Ireland and Australia.

Seven years after his initial collapse, doctors have told Knapp that he can likely take the machine out of his chest and start living like he did before the collapse.

But a lot has changed since that afternoon in the Woodruff gym.

“I’m a smart guy, and I can weigh all the options for myself,” Knapp said. “Ultimately, that’s what I did.”

But it wasn’t Knapp’s option to exercise. The appellate court gave NU the ability to decide. Knapp knew there was a risk — his heart beat fine in one moment, but he could be face down on the court in the next. What no doctor could explain, no doctor could prevent.

Now more than ever, NU understands the importance of precaution. Will’s lawyers have said they will seek “substantial” claims on the damage caused by Wheeler’s death.

Knapp’s disability never stopped him from playing. Like any athlete with an impairment, he played for reasons he said are hard for most people to understand.

“Some people don’t appreciate athletes, their dreams and what it means to them.”