  In this short article, we establish a rigidity theorem for pairs of
hyperquadrics in a weaker sense, i.e., we impose a condition that minimal
rational curves are preserved, which is stronger than inheriting a sub-VMRT
structure, a notion raised by Mok & Zhang (2014). This problem has its source
in a theorem of Tsai (1993), and the main result of this article can be applied
back to give a more intrinsic proof of Tsai's theorem.
