American Venus missed much of last year with injury and had been hoping to break into the world's top 16 by the start of the French Open, which starts on Sunday.
The 26-year-old is ranked 29th but had dropped as low as 71 after wrist and knee injuries.
Rezai will meet American Meghann Shaughnessy in the quarter-finals.
In other second-round action, second seed Elena Dementieva of Russia beat Croatian Jelena Kostanic Tosic 6-3 6-3 to reach the quarter-finals, where she will play Colombia's Catalina Castano.
Dementieva, ranked 14th in the world, said at the start of this month she had considered retirement after suffering a stress fracture of three ribs while working with a new physical trainer in Moscow.
Swiss third seed Patty Schnyder beat American Vania King 6-4 6-1 and will face fifth-seeded Ukrainian Alona Bondarenko in the quarter-finals.
Number one seed Maria Sharapova and Poland's Agnieszka Radwanska will contest the other quarter-final.
