After a productive summer on the hardcourts of their native North America, Kops-Jones and Spears have carried this form across the Pacific, winning their second and third titles of the year in Seoul and Tokyo.
Castaño and Razzano only gained a spot in the draw after the 11th hour withdrawal of Anastasia Pavlyuchenkova and Lucie Safarova, but they certainly made the most of their opportunity, giving the No.8 seeds a real scare before eventually going down, 67(3) 64 105.
Next up for Kops-Jones and Spears will be Daniela Hantuchova and Peng Shuai, who despite playing alongside one another for just the second time impressed during a 63 62 victory over Olga Govortsova and Monica Niculescu.
Lying in wait for the winner of this match are No.3 seeds Ekaterina Makarova and Elena Vesnina after they cruised into the last eight with a 62 63 win over Chinese wildcards Tang Hao Chen and Tian Ran.
Hoping to join them there will be compatriots and No.2 seeds Maria Kirilenko and Nadia Petrova, who, having received an opening round bye, finally kick off their title challenge on Wednesday against the dangerous unseeded team of Jelena Jankovic and Andrea Petkovic.