Austria got on the board, Spain flexed their muscles and Croatia and South Africa's returning stars kept them in the hunt for finals action at the ATP Cup with important wins on the fourth day of competition.
Dennis Novak, ranked 101 in the world, was the unlikely hero in Sydney for Austria, rallying after a talking to from captain Thomas Muster to beat world No.25 Guido Pella 0-6 6-4 6-4.
World No.4 Dominic Thiem then beat good mate Diego Schwartzmann 6-3 7-6 (7-3) to wrap up a must-win victory over Argentina to leave both countries 1-1 and still a chance of sneaking into the quarter-finals.
"After the first set I went to a toilet break with Thomas, and I came out and changed a little bit my game and fought back in the game," Novak said.
"I think at the end I played really good tennis."
Spain continued their dominance in Perth with world No.1 Rafael Nadal and Roberto Bautista Agut cruising to easy wins against their Uruguayan opponents.
Nadal dispatched of world No.45 Pablo Cuevas 6-2 6-1 and Bautista Agut needed less than an hour to see off unranked 19-year-old Franco Roncadelli in a 6-1 6-2 romp.
Novak Djokovic secured an impressive 6-3 6-2 win over world No.9 Gael Monfils to level Serbia's tie at 1-1 with France in Brisbane.
The world No.2's triumph came after Benoit Paire's fiery 6-2 6-7 (8-6) 6-4 defeat of Dusan Lajovic had put the French 1-0 up.
Earlier, Croatia's Marin Cilic, who dipped to No.38 in the world after an knee injury-curtailed 2019, was scratchy but showed his class with a 7-6 (10-8) 6-4 victory over Poland's Kacper Zuk in Sydney.
The Croatians surprisingly dropped their second singles rubber when Borna Coric was outclassed by Hubert Hurkacz 6-2 6-2 but the combination of Ivan Dodig and Nikola Mektic were far too good for Hurkacz and Lukasz Kubot, 6-2 6-1.
The tie takes Croatia to 2-0 for the tournament and in good shape to take out Group E.
South Africa's position in Group A is more tenuous but after dominant singles wins against Chile and a doubles victory to make it 3-0, they can still make the final eight.
Lloyd Harris got the ball rolling in Brisbane with a 6-4 6-4 victory over Nicolas Jarry before the impressive Kevin Anderson downed Cristian Garin 6-0 6-3.
South Africa are 1-1 in Group A, and will likely need to progress as one of the best-performed second placed teams given the Djokovic-led Serbia are in their pool.
Surprise-packets Japan secured their tie against Georgia in Perth to move to 2-0 in Group B but face the might of a Nadal-led Spain on Wednesday.