Colonial First State Global Asset Management (CFSGAM) senior portfolio manager Martin Littler will leave the organisation on 16 September.
The announcement took some analysts by surprise.
"It is certainly sudden and earlier then anticipated," Standard & Poor's fund analyst Andrew Yap said.
"The organisation hasn't given us full disclosure as to why he intends to leave."
Littler already took a step back in February this year from his responsibilities as manager of the Australian equity core team.
But Yap expected at the time that Littler would remain with the company for some time, focusing on the Australian Share Long Short Core Fund.
S&P put the CFS Wholesale Australian Share Long Short Core Fund on hold yesterday.
"While no ratings action is being taken with regard to the team's long-only strategies, we believe Mr Littler's earlier than anticipated departure to be more significant for the team's long-short capability," S&P fund analyst Michael Armitage said.
"As the lead portfolio manager, our conviction was largely attributed to his experience and shorting capability, something that is not fully evident as yet with regard to Mr [Wayne] Gentle, who will assume this role."
CFS denied Littler's retirement was earlier than expected.
"The team has successfully managed a smooth transition of portfolio responsibilities over the past seven months and it's expected they will continue to deliver solid performances for the foreseeable future and remain one of the most respected components of the CFSGAM business," CFSGAM chief investment officer David Dixon said.
"Martin has made a significant contribution to the business over many years and we wish him the very best in his retirement."
Gentle, a CFS senior portfolio manager, will become lead portfolio manager of the CFS Wholesale Australian Share Long Short Core Fund and Dawn Kanelleas, co-portfolio manager for the CFS Wholesale Australian Small Companies Core Fund, will cover the large-cap resources sector.
"We consider the decision to transition Mr Littler's large-cap resources coverage to Ms Kanelleas to be an appropriate interim measure," Armitage said.
"However, this is an extension of Ms Kanelleas's existing responsibilities and we will be closely monitoring the firm's progress as it seeks to appoint an appropriately experienced full-time larger-cap resources analyst."
