A Texas high school football coach made a selfless choice when he decided to donate part of his liver to a colleague.

Matthew Beeler stepped in to help fellow Cypress Ridge coach John McWilliams, who suffers from a debilitating genetic disease. The transplant is scheduled for Thursday.

McWilliams' condition causes his body to attack its organs, and his own liver was being rejected.

"After Thanksgiving, I came in and all the coaches were sitting in there," McWilliams recounted. "And I said, "Hey guys, I need a liver.'"

Beeler admitted that he and McWilliams hadn't known each other for long, but said he felt connected to the coach.

"I said, "Shoot, I couldn't help a nicer man,'" Beeler said. "It wasn't my decision to do it. I feel like I was put here to do it."

Beeler and McWilliams ended up being a perfect match, and underwent the organ transplant on Sunday. Because the liver regenerates, Beeler will donate 63 per cent of the organ to his friend.

The men will miss the rest of the school year, but expect to return in the fall.

Cypress Ridge students are helping with their coaches' medical expenses by selling motivational t-shirts, and a crowdfunding effort was begun through the National Foundation for Transplants.

"For the rest of his life, [McWilliams] will need follow-up care and daily anti-rejection medications," the site read. "Post-transplant medications are very expensive, and they're as critical to his survival as the transplant itself. In addition to his own transplant expenses, John is also raising funds to cover the costs of his donor's out-of-pocket expenses, further increasing his need."

Donation information and more details on McWilliams' medical condition and financial need can be found on the foundation's website. Over $28,000 has been raised of a $100,000 goal.