Tsuba-Zeriyai Like a Standing Wall

During today's keiko w/ NG, I hit his Men (but missed), then, as I ran into him,
I almost was knocked down by his Tsuba-Zeriyai (standing straight w/ Shinai right in front of the face).

From my own (limited) experience, when I run into the opponent after the strike, I could easily bounce back and would do straight Tsuba-Zeriyai w/ the opponent (standing face to face). Then, slowly move back to Kamae.

However, I was shocked by how firm and strong NG stood and he stood straight doing Tsuba-Zeriyai. Then, as he slowly pushed me back, I couldn't stop but had to move back no matter how hard I tried to push him away. It was like trying to push against a moving wall (that's slowly coming toward me).

After the practice, I asked NG how he does Tsuba-Zeriyai. He said that he puts his weight on the lower body, bending his legs a little. I tried to follow that but couldn't quite grasp it.

I'll try to practice it and learn more from him, then post my progress as I go.

p.s. I mispelled Tsuba-Zeriyai, too! I thought it was Tsuba-Zeri. I'll correct it from now on.