Matt Comyn is now searching for six new members of his executive team after the poorly timed departure of chief financial officer Rob Jesudason, who is heading back to Hong Kong after less than a year in the job.

Jesudason has landed a role at Hong Kong start-up called Block.one, which is, as the name implies, a blockchain and cryptocurrency firm – not exactly a Big Four bank.

While much has been made of the fact Jesudason is keen to eventually test his skills as a chief executive, he will be chief operating officer in his new gig.

Commonwealth Bank chief executive Matt Comyn faces a tough task to replace so many executives. Peter Braig

While it feels like this is a very sudden step sideways for Jesudason, it is worth noting he was based in Hong Kong in his previous CBA role as group executive for International Financial Services. Sources say his family hadn't really settled in Australia and favoured a return to Hong Kong.

CBA insiders say Comyn and Jesudason decided it was better for the CFO to go now, before his six biggest weeks of the year, when the June 30 accounts need to be prepared. It is understood Comyn felt a clean break was smart for all.