Novak Djokovic maintained his perfect start at the ATP Cup to help Serbia reach the quarter-finals, with the world number two improving to three singles wins and one doubles victory from four matches.
Djokovic, who has yet to drop a set at the tournament, beat Chile's Cristian Garin 6-3 6-3 in Brisbane.
Dusan Lajovic earlier broke Nicolas Jarry three times en route to a 6-2 7-6 (3) win, as the Serb finished the round-robin stage with a 2-1 singles record.
Serbia won Group A on Monday and, despite a loss doubles against Chile, will travel to Sydney to compete in the top eight.
Spain also progressed in Perth after world number one Rafael Nadal beat Japan's Yoshihito Nishioka 7-6 (4) 6-4 in a gruelling battle over two hours and eight minutes in Perth.
Nadal's team-mate Roberto Bautista Agut beat Go Soeda 6-2 6-4 as Spain topped Group B and set up a last eight tie in Sydney on Friday.
Poland beat Dominic Thiem's Austria to finish second in Group E, with the world number four losing 6-3 6-4 7-6 (5) to Hubert Hurkacz.
Later, France takes on South Africa in Brisbane, Georgia meet Uruguay in Perth and Marin Cilic's Croatia battle Argentina in Sydney.