Mitchell Stack, director of debt investments at the Future Fund, is leaving to join Bain Capital’s Sankaty Advisors, which manages some of the fund’s high-yield investments.

Stack joined the Future Fund in 2007 from US bond firm, Western Asset Management, and has built the debt team within the Future Fund.

Boston-based Sankaty manages just under $20 billion in distressed debt and credit, and is one of seven high-yield managers of “distressed-debt and event-driven” portfolios retained by the Future Fund, which allocates $14 billion of its $80 billion under management to distressed debt.

Last year Stack was reported to be leaving the fund to head up the Australian operations of Ares Management, which also services the Future Fund.

The departure is believed to be amicable and the Future Fund released a statement wishing Stack well.

“We’re sad to see Mitch go after his five years with us,” a spokesman said. “He’s done an excellent job of building a talented team and an innovative portfolio that has performed very strongly in a challenging environment.”