Roberto Bautista Agut has continued his impressive start to the year, taking the scalp of world No.8 Casper Ruud to seal Spain's ATP Cup tie against Norway.
Bautista Agut, the world No.19, beat the rising star 6-4 7-6 (7-4) after countryman Pablo Carreno Busta had eased through his singles match, 6-3 6-3 over world No.345 Viktor Durasovic.
Their win, without Rafael Nadal, followed an opening-day clean sweep of Chile where Bautista Agut dominated world No.17 Cristian Garin 6-0 6-3.
Fellow top-10 talents Matteo Berrettini (No.7) and Daniil Medvedev (No.2) have already been upset at the Sydney teams tournament.
And Polish star Hubert Hurkacz looked to be joining the list, dropping the first set to world No.570 Aleksandre Metreveli.
Last year's Wimbledon semi-finalist held his nerve though in a tense 6-7 (7-5) 6-3 6-1 win that clinched the win for Poland, who along with Spain are now unbeaten from two ties.
Greece's world No.4 Stefanos Tsitsipas is scheduled to play his first singles match of the year later on Monday night against Argentina's Diego Schwartzman.
Tsitsipas pulled out of his top-10 battle with Hurkacz on Saturday, the Greek favourite wary after having surgery on his elbow in November.
Serbia and Chile meet in the other tie on Monday night.
