Spain have emerged as the biggest threat to Russia's ATP Cup title defence after powering through the group stages unbeaten.
Spain secured their semi-final spot with a 2-1 win over Serbia in Wednesday night's Group A decider in Sydney.
They only needed to win one match to advance and Pablo Carreno Busta wasted little time claiming the required rubber.
The two-time US Open semi-finalist outclassed Filip Krajinovic 6-3 6-4 in little more than an hour to book Spain a semi-final showdown with Poland.
Having already clean swept Norway and Chile, Spain couldn't be stopped from topping the group even if they lost the tie to Serbia.
But, for good measure, Roberto Bautista Agut clubbed Dejan Lajovic 6-1 6-4 to seal a comprehensive victory for Spain.
Nikola Cacic and Matej Sabanov gained a consolation point for Serbia with a 6-7 (5-7) 6-3 10-5 doubles win over Albert Ramos-Vinolas and Pedro Martinez.
Poland earlier clinched their place in the knockout stages for the first time after sweeping Argentina 3-0.
World No.9 Hubert Hurkacz sealed the tie with an impressive 6-1 6-4 win over the 13th-ranked Diego Schwartzman.
World No.117 Kamil Majchrzak had earlier banked his third singles win in a row by accounting for the higher-ranked Federico Delbonis 6-3 7-6 (7-3).
Hurkacz and Majchrzak have dropped just one set in singles this week, also beating fancied teams from Greece and Georgia.
Chile defeated Norway 2-1 in Wednesday's Group A dead rubber.
World No.8 Casper Ruud levelled the tie for Norway with a 6-4 6-1 defeat of Christian Garin after Alejandro Tabilo downed Viktor Durasovic 6-1 6-7 (7-5) 6-1 to draw first blood for Chile.
But the 167th-ranked Tabilo then teamed up with Tomas Barrios Vera to clinch the tie with a 6-0 6-4 doubles win against Leyton Rivera and Andreja Petrovic.
The unbeaten Russians face Italy (1-1) on Thursday, while Lleyton Hewitt's Australian team (1-1 but out of mathematical contention) chase some pride and Australian Open lead-up form against winless strugglers France (0-2) in a dead rubber.
The Group C semi-final spot remains up for grabs, with Great Britain (1-1) playing the USA (1-1) in the day tie at Qudos Bank Arena and Germany (1-1) and Canada (1-1) squaring off in the Thursday night session.
A countback could well be needed to determine who meets Russia or possibly Italy in the semi-finals.