Chris Seitz, a goalkeeper for FC Dallas, entered his name in the national bone marrow registry in 2008. In August, he received an email that he was a match for a patient. Seitz recorded a video diary for ESPN.com to help people understand the experience. (2:56)

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ALLAS -- At the moment when everything changed, when life became about more than stopping shots and winning soccer matches, FC Dallas goalkeeper Chris Seitz was where you could always find him on a mindless weekday afternoon: sitting in his office playing a testosterone-filled game of "Halo."

FC Dallas goalkeeper Chris Seitz Stephen Dunn/Getty Images

The most important two hours of his day were over, a training session in which he pushed his body as hard as he could with the simple goal of improving. This was his life, that of a backup, where practice was often more important than the game. But now that work was over, it was time for play. Seitz and three of his teammates had met online and were hunting a group of strangers in a virtual reality. The task was simple: kill or be killed.

In the middle of it all, Seitz's phone vibrated. He first ignored the new email, then put his controller down and began to read. He couldn't believe the words staring back at him. "Bone marrow?" "Donor?" "Match?" Huh?

Four years ago, Seitz and his then teammates at Real Salt Lake -- along with hundreds of others in the tightly-knit MLS family -- registered to become bone marrow donors. It was a show of solidarity for Salt Lake midfielder Andy Williams' wife, Marcia, who was battling a rare form of leukemia.

In the years since, Seitz would receive a monthly newsletter from DKMS, the bone marrow center where he registered, and would delete it. But this email was different. This email involved a total stranger who needed help.

"Guys," Seitz said to his Dallas teammates online, "something has come up. There's this email. I gotta go."

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n the world's most popular game, the role of the goalkeeper is that of savior. He is the one called upon when all other measures of defense fail. When a team has sliced its way through all 10 members of the opposition, it's on the keeper to jump, dive, kick, roll -- do anything and everything he can -- to keep the ball out of the back of the net. Do this well and you're a hero, an international soccer god. Fail and you'll quickly find yourself searching for a new goal to guard.

In the six years Seitz has played professional soccer, he has spent more time looking for a new home than any keeper would like. He came into the league in 2007 with all sorts of promise -- leaving the University of Maryland after his sophomore year to become the No. 4 overall pick in the MLS SuperDraft. There were those who suggested he had the highest ceiling of any American-born keeper to join MLS. But in the six seasons since, Seitz has played for three organizations and has failed to keep the starting job with any of them. He came closest in 2010, starting 22 matches for the expansion Philadelphia Union, but posted a 1.80 goals-against average, the highest mark that season for any keeper with more than one start.

Chris Seitz joined FC Dallas in 2011. Tom Pennington/Getty Images

The past two seasons in Dallas, he has backed up veteran Kevin Hartman while trying to learn and improve every day. Coaches say he has rarely sulked or complained and has instead built a reputation as a friendly, laid-back guy who is always trying to get better. It makes sense. These were the lessons taught by his mom and dad while he was growing up with his older sister, Caitlin, in the central California town of San Luis Obispo.

This past April, when Hartman suffered back spasms minutes before a match against Vancouver, Seitz stepped in and held the Whitecaps to just one goal in a 1-1 draw. A week later against the high-powered Landon Donovan- and David Beckham-led L.A. Galaxy, Seitz did the same in another 1-1 match. But after a five-game stint filling in for Hartman, he went back to the bench, back to rebuilding his career through practices, reserve matches and friendlies.

"It's tough for backups," he said. "But I really thought I had improved. I was starting to play well. The team was eyeing the playoffs. Then I got that email."

It was early August. The team had rebounded from a 14-match winless streak and was starting a push for the playoffs. Then everything changed. The email had come from DKMS, the largest bone marrow donor center in the world. The organization was founded in 1991 in Germany as "Deutsche Knochenmarkspenderdatei," which translates to German Bone Marrow Donor Center. DKMS Americas was founded in 2004.

The email explained that Seitz's name had appeared in the center's database as a potential match for a dying patient. It asked him to contact them as soon as possible if he wanted to help. The timing couldn't have been any more extraordinary.

In a little more than a week, Seitz's dad was scheduled to become a donor for the goalkeeper's uncle, who had been diagnosed with leukemia in January. Through a process called apheresis, doctors would remove blood from a vein in one of Michael Seitz's arms and send that blood through a separator to remove blood-forming cells and then re-inject the remaining blood into the other arm while the cells would go to the recipient.

"It was an amazing coincidence," Seitz said.

As he dialed the DKMS phone number, Seitz thought about the Sunday night family dinners he and his family had with Uncle John and his cousins and their grandma growing up. And he thought about Marcia Williams. In 2008, Seitz had been in his second year with Real Salt Lake when he watched the wife of popular teammate Andy Williams struggle with her own leukemia fight. The disease is the second-leading cause of cancer deaths in the United States. Marcia was the reason Seitz had agreed to have one of his cheeks swabbed to join the registry. She was the reason he had once worn a faded green "Soccer Unites Utah" wristband.

Now he found himself on the phone with a DKMS representative, listening to the woman explain that, if he was interested, he might have the opportunity to help save someone like Uncle John or Marcia.

"I told her I was in the middle of my season," Seitz said. "I told her I'd be willing to do everything I could but I needed more information. I couldn't just go to my team without knowing exactly how this would all work."

The woman told Seitz he was getting ahead of himself. He might not be the only match. He might not be the best match. A blood test would be needed to find out. Two weeks to a month after that, DKMS would call Seitz with an answer.

"Ten days later, the phone rang," Seitz said. "They told me I was by far the best match."

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he next day, Seitz walked into the office of FC Dallas coach Schellas Hyndman and asked for permission to leave the team. Up to that point, the only person Seitz had spoken to in the organization was trainer Skylar Richards. They had agreed to keep the subject to themselves, figuring there was no need to worry the team if Seitz wasn't even a match. But now that he was, they knew they couldn't keep quiet anymore.

"You never know how people are going to take something like that," Seitz said. "It's a business, after all. This has the potential to hurt them. But at the same time, it's about more than just a game. You just hope they'll back you."

DKMS told Seitz that because of the type of cancer his recipient had, the less invasive donation procedure his dad went through wasn't an option. Instead, Seitz would require surgery in which doctors would poke two holes in his lower back, then fish 32 needles through each of those holes to remove fresh marrow from the core of Seitz's bones. Doctors would then inject that marrow into the recipient.

For an average 25-year-old, the procedure might mean a few days of discomfort and a week or two of decreased activity. For a professional goalkeeper, who makes a living diving on the exact bones where the marrow would be extracted, the situation was far more precarious.

Chris Seitz started 22 matches in 2010 for the Philadelphia Union. AP Photo/Matt Slocum

"He dives on his hips. So much force is distributed through that area," said Richards, the Dallas trainer. "So many back muscles attach down there. If he dives too early, he could get a hip fracture. If he pushes it too soon, he could get a stress fracture. There's a lot to be concerned about."

Further complicating matters was the fact that, for a professional athlete, this was uncharted territory, at least for DKMS. The donor center, one of more than 50 affiliates of the National Marrow Donor Program, said Seitz is the first professional athlete in its registry to become a donor while his sport is in season.

With no previous information to rely on, Richards sought the input of various doctors, trainers and nutritionists to put together a plan for Seitz's recovery. The two of them met with the team that would do the procedure to learn the ins and outs and exactly what was going to happen. Richards then built a day-by-day rehab program that, if all went according to plan, they hoped would allow Seitz to return to the field for Dallas' season finale on Oct. 28.

They presented all their research to Hyndman. And then they listened.

"As Chris spoke, I wanted to cry," Hyndman said later. "You have people who won't even donate blood. They drive right by the blood bank. And here's this guy willing to get on an airplane and go through an elective surgery to try and save the life of someone he doesn't even know. And it might not even work.

"Of course I wanted to do everything I could to make this happen."

But at the same time, Hyndman knew better than to make an emotional decision without talking to ownership. And he knew the team would need to find a capable replacement before it could green-light Seitz's departure.

"When I said that, you could see the hesitation on [Seitz's] part," Hyndman said. "He made this eye gesture as if to say, 'You mean this might not work?' You could see in his face how much he wanted to do this."