Moscow - Nick Kyrgios said he was "surprised" to be cheered by the home crowd as he beat Russian youngster Andrey Rublev 6-3, 4-6, 6-4 in the Kremlin Cup first round on Tuesday.
The temperamental Australian, seeded fifth in Moscow, fired 24 aces to win his first-ever meeting with the 20-year-old Rublev.
"I love to play indoors and we played a lot with Andrey in juniors. He's going to have a great career," Kyrgios said.
"I was surprised that the public cheered me here. It's nice. Normally when I'm not at home I'm not the most loved person but it was nice to hear some cheering. I felt almost at home here."
The 23-year-old Kyrgios, who has slumped to 37th in the world rankings after struggling for form and fitness this year, will meet Mirza Basic in the last 16, after the Bosnian saw off Tunisia's Malek Jaziri 7-6 (7/4), 6-2.
Reigning champion Damir Dzumhur saw his title defence come to an abrupt halt with a first-round loss to Belarusian qualifier Egor Gerasimov.
The Bosnian, who won both the St Petersburg and Moscow tournaments last year, slumped to a 6-1 6-7 (5/7), 6-2 loss to the world number 217.
Gerasimov will next face charismatic Frenchman Benoit Paire for a place in the last eight.
Paire, who has not reached a quarter-final since February, beat Mischa Zverev 7-6 (8/6), 2-6, 6-1.
"It was a good match. I wasn't doing well at the beginning but then I got much better," Paire said.
In the women's draw, former world number two Vera Zvonareva set up a second-round meeting with second seed Karolina Pliskova.
The 34-year-old Zvonareva, a two-time Grand Slam finalist, saw off fellow Russian qualifier Irina Khromacheva 6-3, 6-3.
Top seed Simona Halep, who secured the year-end world-number-one ranking on Monday, pulled out of the tournament earlier on Tuesday to rest a troublesome back injury.
"While it's disappointing to withdraw, I know it's important to put my health first," she said.
Results from the ATP/WTA tournament in Moscow on Tuesday (x denotes seeding):
Benoit Paire (FRA) bt Mischa Zverev (GER) 7-6 (8/6), 2-6, 6-1
Egor Gerasimov (BLR) bt Damir Dzumhur (BIH x6) 6-1, 6-7 (5/7), 6-2
Evgeny Donskoy (RUS) bt Mikhail Kukushkin (KAZ) 6-4, 7-6 (12/10)
Andreas Seppi (ITA) bt Martin Klizan (SVK x8) 6-1, 7-6 (8/6)
Nick Kyrgios (AUS x5) bt Andrey Rublev (RUS) 6-3, 4-6, 6-4
Mirza Basic (BIH) bt Malek Jaziri (TUN) 7-6 (7/4), 6-2
Ricardas Berankis (LTU) bt Denis Istomin (UZB) 6-4, 5-4 - retired
Dusan Lajovic (SRB) bt Filip Horansky (SVK) 6-4, 2-6, 6-3
Alize Cornet (FRA) bt Natalia Vikhlyantseva (RUS) 5-7, 6-2, 7-5
Daria Gavrilova (AUS) bt Vitalia Diatchenko (RUS) 7-6 (7/5), 7-5
Johanna Konta (GBR) bt Elise Mertens (BEL x7) 6-3, 7-5
Kristina Mladenovic (FRA) bt Anna Kalinskaya (RUS) 6-1, 6-3
Ons Jabeur (TUN) bt Ekaterina Makarova (RUS) 6-1, 6-2
Vera Zvonareva (RUS) bt Irina Khromacheva (RUS) 6-3, 6-3