Sally Macdonald's departure from Big W after less than a year will slow the turnaround of the discount department store chain, and increase the likelihood Woolworths will sell the troubled business.

Retail analysts claim the shock departure of Ms Macdonald also risks disrupting the main game at Woolworths - the turnaround of Australia's biggest supermarket chain.

Embattled Big W chain is facing more upheaval as Woolies is working to turn around its fortunes. Credit:Glenn Hunt

"The key thing for Woolworths remains food and the risk is this takes a bit of the shine off food," one analyst said.

"This was always a long-dated turn around, this business is really challenging and it as always going to take a long time."