Port Adelaide chief executive John James quits to take on a lucrative position with American funds management company Vanguard based in Philadelphia.

"I certainly feel mixed emotions because I want to be part of the solution, and I will do anything I can in the time I have left at the club," John James said of the Power who are struggling to perform on the field.

"The frustrating thing is internally we run such a great business and a great organisation and the external pressure is we haven't performed on-field as we'd have wanted to, but internally we're rock solid."