41-year old Tim Duncan walked away from the game of basketball after the 2015-16 season, and in typical Tim Duncan fashion, we haven't heard much of him since.

That's because he has quietly been morphing into a 7-foot killing machine.

Earlier this week, the Echols Fitness Facebook page shared a 23-second video of The Big Fundamental working on his MMA technique with a sparring partner. As it turns out, Duncan has been training with Echols Fitness for more than eight years now, and the Muay Thai and kickboxing training helped him stay in shape in the offseason.

A statement from Tim Duncan on the Echols website reads,

“Training with Jason for the last 8+ years has transformed the way I prepared in the off seasons.  Now that it is all off season I use my work with him to stay physically and mentally strong, while learning a challenging skill and having fun doing it.  When you can combine a mental challenge with physical workout you forget you are working out and makes you want to come back for more.”

Check out the footage below.