Ex-NFL star Greg Olsen says his 8-year-old son is absolutely crushing it in the weeks following his heart transplant ... calling his recovery process "unbelievable."
As we previously reported, Olsen's son, TJ, -- who was born with a congenital heart disease -- underwent the serious surgery earlier this month to receive a new heart.
The Olsens have been documenting TJ's story every step of the way ... including the special moment when he "rang the bell" to symbolize the end of his treatment 2 weeks ago.
Now, Greg is sharing even more good news .