The Port Adelaide assistant will be unveiled as coach after holding talks with the St Kilda coaching panel on Wednesday night, according to reports in Fairfax Media.
The meeting came after Richardson backflipped on his previous comments on Tuesday that he was very happy at Port, by flagging his interest in having an interview with the Saints to replace Scott Watters, who was sacked by the Saints earlier this month.
Earlier on Wednesday the Saints officially denied a report that Richardson had been appointed as the Saints' new senior coach.
Until Richardson's change of heart regarding his interest in the position, Richmond senior development and former Port coach Mark Williams was regarded as the hot favourite to succeed Watters.
Port Adelaide chief executive Keith Thomas was disappointed with the timing of the appointment, saying it left the Power in a tough position to replace the highly rated assistant.
"It's a bit deflating," Thomas told The Age.
"I am genuinely dismayed about the lateness of the process and the position it now puts us in. We will now get on with it and ultimately let it go. He (Richardson) understands that, he doesn't feel good about it but it's an opportunity he felt he had to pursue.
"Something clearly changed. He has assured us he was not talking to St Kilda prior to yesterday although his manager had been in regular contact and I think what it showed us is that he harboured ambitions to be a senior coach and that is something we could not compete with."
Richardson was one of three candidates interviewed for the St Kilda job that was given to Watters in 2011, coincidentally also including current Power coach Ken Hinkley.