The 36-year-old tight end made the announcement on his social media page Friday morning, calling the news "a huge step forward."

"A day we have prayed for has arrived," Olsen said while posting a picture of him smiling with TJ and his wife, Kara.

"We were alerted last night that there was a donor match for TJ to receive his heart transplant. Walking our little boy, with tears of hope and fear in our eyes, was one of the toughest moments of our lives."

Olsen added, "We ask for everyone’s prayers for TJ and his amazing team of doctors and nurses. TJ has a long road ahead of him but today is a huge step forward."

As we previously reported, TJ was hospitalized last month in North Carolina with a serious heart condition.

Olsen said it was all very terrifying, 'cause TJ "has already undergone 3 open heart surgeries and has survived with a modified heart for his first 8 years of life."

It's unclear when TJ will have his operation ... but he's already got at least one big NFL star rooting for him -- Julian Edelman tweeted to Olsen on Friday, "Thoughts are you with your little one today bubs."