Lleyton Hewitt won 6-2, 6-1, 4-6, 7-6 (2) over China's Zhang Ze to give Australia an unassailable 3-1 lead in the Asia-Oceania second-round match.
The 173rd-ranked Hewitt, originally only listed to play in Saturday's doubles, replaced Marinko Matosevic for the first of Sunday's reverse singles.
The former No. 1-ranked Hewitt repaid the faith of team captain Pat Rafter, recording his 37th win in 46 Cup singles matches.
On Saturday, Hewitt helped give Australia a 2-1 lead after a straight-sets win in doubles with partner Chris Guccione.