Skateboarding superstar Nyjah Huston says he understands the pressure Simone Biles is going through at the Olympics ... telling TMZ Sports people need to realize athletes are human, not emotionless robots.
Biles shockingly withdrew from the gymnastics team finals on Tuesday ... citing her struggles with mental health affecting her performance.
Huston -- who just landed on U.S. soil after competing for Team USA at the Tokyo Games this week -- can relate to the expectations of being the best in a sport .