NFL players, perhaps moreso than their counterparts in other sports, are used to playing through pain. Nicks and bruises come and go. Muscle sprains and pulls linger.

Few players, however, have to deal with the sort of pain that affected Jesse Sapolu, the former San Francisco 49ers offensive lineman and four-time Super Bowl champion. Sapolu played the majority of his 15-year career with a torn aortic heart valve that at times left him so short of breath that he felt like he was drowning.

If this comes as a surprise to you, you’re not alone. Sapolu never complained about his condition, and he even tried to hide it from his team. An offensive lineman through and through, Sapolu knew his accomplishments spoke louder than words ever could. Only recently has Sapolu divulged the extent of his heart condition, in his new book "I Gave My Heart To San Francisco."

"I quietly went about doing my job and doing it to the best of my ability because I was very thankful for the opportunity," Sapolu tells ThePostGame. "When I was growing up, I never even thought I would have this opportunity to play on the big stage."

Sapolu first began feeling the effects of his torn aortic valve when he was 7, and he distinctly remembers struggling to breathe during a rugby game in his native American Samoa. The torn valve was caused by rheumatic fever, a condition that Sapolu had developed a few years earlier.

Without much in the way of medicine, as a child Sapolu relied on massages to alleviate the pain from his swollen legs. But the tear, and the heart valves' inability to close completely, forced Sapolu's heart to work harder and grow to become much larger than it normally would be. As a grade schooler, Sapolu was forced to sit out recess because of his condition, and he was denied the opportunity to play on certain sports teams.

He never forgot the empty feeling of watching from the sidelines.

"That hurt me so much that as I got older, whenever I would feel symptoms of my condition, I would not ever complain about it," Sapolu says. "I carried myself through my career that way."

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At certain points during practice or conditioning in San Francisco, Sapolu recalls the chest pain becoming so acute that he could hardly breathe. Despite trying to keep his condition a secret from the team when he was drafted in 1983, the 49ers soon found out and ordered Sapolu to make regular visits to a cardiologist at Stanford.

Doctors told Sapolu that he could have taken blood thinners to help lessen his pain, but that would increased his risk of bruising and blood clots and likely shortened his career. Instead Sapolu played on, and late in his career his heart condition became so poor that one doctor said the leak in his heart was worse than that of an 80-year-old-man.

Eventually, however, Sapolu was able to use his condition as a mental advantage. The fact that he was even able to step onto an NFL field was such an improbability that he figured he had nothing to lose.

"When the nerves hit, I would conjure up ways to get rid of that nervousness," Sapolu says. "I would always say to myself, 'You’re not even supposed to be here, why are you nervous?' Just go out and let it go.'"

Sapolu had two heart surgeries, in 1997 and 2011. He recently traveled back to Hawaii and Samoa in hopes of educating people about his disease. If the condition is identified early enough, proper treatment can prevent an enlarged heart. Sapolu wasn’t so fortunate, but at least he can rest easy knowing that he put his big heart to good use.

-- To order Sapolu's book or to see his book signing schedule, please visit