Hilfenhaus plays for Hobart Hurricanes, while Smith represents Adelaide Strikers.
Melbourne: Australians Ben Hilfenhaus (Hurricanes) and James Smith (Strikers) have been ruled out of the remainder of the Big Bash League (BBL) with injuries.
They will be replaced by Mark Higgs (Hurricanes) and Travis Head (Strikers), respectively, Cricket Australia (CA) announced Wednesday.
The Twenty20 BBL technical committee approved the changes to the Hobart Hurricanes and Adelaide Strikers squads.
Higgs is a former New South Wales and South Australia player who toured for Australia for an International Cricket Council (ICC) event in Kenya in 2000.
Head represented Australia at last year's ICC Under-19 World Cup and been a regular member of South Australia's Bupa Sheffield Shield team this summer, highlighted by a top score of 95 not out against Western Australia.
Both Higgs and Head are available for selection in their teams' last round matches.