The rank of random regular digraphs of constant degree

Let d be a (large) integer. Given n≥2d, let An be the adjacency matrix of a random directed d-regular graph on n vertices, with the uniform distribution. We show that the rank of An is at least n−1 with probability going to one as n grows to infinity. The proof combines the well known method of simple switchings and a recent result of the authors on delocalization of eigenvectors of An.