UnitedHealth said on Thursday it will replace its finance chief John Rex with an external hire, Wayne DeVeydt, adding to the management changes at the health insurer that has been struggling to control its medical costs.

Wayne DeVeydt, a healthcare veteran who most recently worked at Bain Capital, will take up the finance chief job on Sept. 2 as the healthcare behemoth faces an array of operational challenges.

UnitedHealth Group (NYSE:UNH) said on Wednesday that it has appointed Wayne S. DeVeydt as its CFO, who will be replacing the current CFO, John F. Rex, effective September 2. This move comes months after former CEO,