The fund was rated three stars.
Hannon, who was also a partner in the firm, left after last year's restructuring of the domestic property securities team.
Goldman Sachs JBWere chief investment officer Andrew Cooke will take over portfolio management duties for the fund in addition to his multi-asset class responsibilities and overall management of the firm's domestic asset class teams.
Cooke will be assisted by property securities analyst Marcus Ryan and Angus Bell, who is a member of the multi-asset class team.
S&P said it considered the changes to be detrimental to the management of the fund.
"S&P has concerns about the manager's ongoing commitment to the asset class and this fund," S&P analyst Peter Ward said.
"Mr Hannon's departure follows the resignation of the fund's former co-portfolio manager, Andrew Smith, in October last year, which saw the fund rating downgraded from four stars to three stars.
"S&P will be seeking to re-rate the fund as soon as possible with a view to resolving the on hold status."
