PARIS (AP) Serbia, Australia, France and Belgium are one win away from reaching the Davis Cup semifinals after winning their two singles matches on Friday.
In Belgrade, Serb Novak Djokovic returned in style after an elbow injury, sweeping past Albert Ramos Vinolas of Spain 6-3, 6-4, 6-2 on indoor hard courts.
''I'm very satisfied with my play, especially my serve,'' said the second-ranked Djokovic, who withdrew from the recent Miami Open because of a right elbow injury.
Troicki will be back on court to team up with 40-year-old Nenad Zimonjic in doubles against Marc Lopez and Jaume Munar. A win will send Serbia through to a September semifinal against France or Britain.
In Brisbane, Australia took charge against the United States, also on hard courts, at Pat Rafter Arena.
Nick Kyrgios finished off John Isner in a battle of the big servers with his 20th ace to win 7-5, 7-6 (5), 7-6 (5) after Jordan Thompson upset Jack Sock 6-3, 3-6, 7-6 (4), 6-4.
Australia can advance to a semifinal against Italy or Belgium with a win in doubles when Sam Groth and John Peers face Sam Querrey and Steve Johnson on Saturday.
''Hopefully we can close it out tomorrow, it's been an unbelievable day,'' Kyrgios said. ''(Isner's) one of the best servers in the world, a proven player.''
Back in Europe, it was an easy day for France on indoor clay in Normandy.
After 17th-ranked Pouille beat Kyle Edmund 7-5, 7-6 (6), 6-3, Jeremy Chardy swatted aside Dan Evans 6-2, 6-3, 6-3.
''The atmosphere was great,'' Pouille said, praising the home support at the Kindarena in Rouen. ''I really wanted to start the weekend well.''
Edmund, ranked 47th, was filling in for top-ranked Andy Murray, whose absence with an elbow injury was keenly felt.
In Saturday's doubles, Julien Benneteau and Nicolas Mahut face British pair Dominic Inglot and Jamie Murray.
Britain won the Davis Cup in 2015, while France has not won since 2001.
Following a tricky start, Belgium took control against Italy on indoor hard courts at the Spiroudome de Charleroi.
Steve Darcis rallied to beat Paolo Lorenzi 6-7 (3), 6-1, 6-1, 7-6 (4) for his 21st win in Davis Cup singles.
David Goffin had an easier time against veteran Andreas Seppi, advancing 6-4, 6-3, 6-3 for his 12th win in the last 13 matches. His only loss during that stretch was against Andy Murray in the 2015 final.
''I needed to find my rhythm and control the rallies,'' the 14th-ranked Goffin said. ''It was a really nice atmosphere, the stadium is amazing. I am really looking forward to tomorrow and hopefully we will finish with a victory.''