Morningstar has downgraded its rating on a BlackRock Australian equities fund following the departure of key staff.

The research firm has given the BlackRock Scientific Australian Shares Fund strategy an "investment grade" recommendation. The fund's previous recommendation was "highly recommended".

"We can't maintain the same conviction level in BlackRock's scientific Australian equities strategy at present after the departure of a number of key team members," a Morningstar report said.

The departures included the resignation of portfolio managers Glen Harris and Nick Burt. Global chief investment officer of the strategy, Morry Waked, also announced his resignation last month.

Following the changes, BlackRock reshuffled the team and appointed Andrew Jackson as head of Australian investments. David Walsh will also take over the portfolio management duties following Waked's resignation.

Walsh has worked for the firm since 2000, a period which included years with the recently merged Barclays Global Investors (BGI). At BGI he was a senior strategist for all international equity strategies.

The firm has also internally appointed Paddy McCrudden into the Australian scientific active equities team to work with Walsh.

McCrudden has been with BGI since 2001.

The new team will need to prove itself following the key departures, Morningstar said. However, the report said the inclusion of the Melbourne-based BlackRock quantitative team means adequate resourcing is in place.

"We will be watching the integration and development of the new team closely and revisiting our opinion of the BlackRock Australian shares strategy in mid-2010," the report said.

Standard & Poor's (S&P) has maintained its rating on the BlackRock fund.

"S&P considers Mr Walsh to be an investment professional with strong technical capabilities, who has been integral in a number of research projects while with BGI," S&P said.