Rybakina and Vukov worked together for five years, before they ended their partnership - which resulted in a Wimbledon title and an Australian Open final appearance - before last year's US Open.
Vukov was slapped with a provisional ban by the WTA last year after US legend Pam Shriver - Donna Vekic's coach - went public with her belief he was in breach of tour rules.
The world No5 then named Vukov as part of her team earlier this year - despite his provisional ban preventing him from obtaining accreditation for the Australian Open.
The Women's Tennis Association has suspended Stefano Vukov, 37, for a year over his alleged behaviour - but refused to disclose details of their investigation.
Last year, Russian journalist Sofya Tartakova told the Tennis Bolshei YouTube channel about "psychological problems" Vukov had caused.
