If Mr Vizard does not appear as a witness for Westpac in its September case to recover $3 million from Mr Hilliard, the bank could pursue him under a deed of settlement he signed in December 2000.
Under the deed, Westpac agreed to reimburse Mr Vizard for money he said Mr Hilliard had stolen.
In return, Mr Vizard agreed to cooperate with any attempts by the bank to recover the funds.
There was speculation this week that Mr Vizard would try to avoid the witness box after he spoke to Victorian police about a perjury investigation relating to evidence he gave at Mr Hilliard’s 2003 committal hearing.
Mr Vizard’s spokesman Mike Smith said on Thursday that if Westpac called Mr Vizard as a witness “that would raise some issues”.
Last year, Victorian authorities dropped criminal theft charges against Mr Hilliard after Mr Vizard, their chief witness, told them he would refuse to answer some questions on the grounds of potential self-incrimination.