Perth - World No 5 Daniil Medvedev backed his attacking instincts and came from behind to beat Fabio Fognini, as Russia swept Italy on the opening day of the inaugural ATP Cup on Friday.
The US Open finalist overcame a sluggish start to prevail 1-6, 6-1, 6-3 in one hour and 47 minutes after world No 17 Karen Khachanov had cruised to a 7-5, 6-3 win over Stefano Travaglia.
"Not happy with some moments of my performance but happy to get the win for my country," Medvedev said. "Fabio destroyed me in the first set. I knew I had to play much more aggressively in the second set and it worked very well."
Medvedev and Khachanov combined to beat Paolo Lorenzi and Simone Bolelli 6-4, 6-3 in the doubles.
Russia have made the early running in Group D alongside surprise packets Norway, who stunned the United States with a 2-1 upset victory.
Medvedev received a code violation in the middle of the first set after thumping a ball into the stands. When world number 12 Fognini cruised through the set with exquisite timing and pinpoint accuracy the overwhelmed Russian looked likely to boil over again.
Instead an aggressive Medvedev found his rhythm and hit the lines to move his diminutive opponent around the court.
Fognini, 32, appeared weary having only arrived in Perth on Thursday following the recent birth of his second child.
Khachanov also started slowly but proved too strong for Travaglia, who was representing his country for the first time.
Travaglia, ranked 84, surprisingly gained an early stranglehold against an error-strewn Khachanov to lead 5-2, but was unable to close twice on his serve. The 23-year-old made him pay and reeled off five straight games to claim the first set with a sizzling backhand winner.
Khachanov needed just one break in the second set to put Russia into the lead.
Earlier, emerging youngster Casper Ruud notched the biggest victory of his career after beating big-serving John Isner to spearhead Norway's victory over the highly-favoured United States.
The 21-year-old levelled the tie with a 6-7 (3/7), 7-6 (12/10), 7-5 beat the world No 19 in two hours and 43 minutes.
He saved two match points in the second set and weathered 33 aces from Isner, after Taylor Fritz thrashed Viktor Durasovic 6-2, 6-2 in the opening match.
Ruud then backed up that victory in the decisive doubles alongside Durasovic, beating Rajeev Ram and Austin Krajicek 4-6, 6-3, 10-5 and trigger jubilant scenes from the Norwegian contingent, who were the last team to qualify for the 24-nation event which is also being played in Brisbane and Sydney.
"I didn't have much time to recover from my singles," Ruud said. "I was a little bit low (on energy) but I got the feet going and we played great. The players are super proud to beat the US."
The world No 54 has risen up the rankings over the past year since training alongside Rafael Nadal at the world number one's academy in Mallorca.
The new tournament replaced the Hopman Cup, a popular annual mixed-teams fixture in Perth for three decades.