Seventh seed Carlos Berlocq had to dig deep Tuesday to eliminate local wild card Andrey Kuznetsov, ranked 67 , in the Kremlin Cup first round.
The Argentinian surged back after being thrashed in the first set to snatch a 1-6, 6-4, 6-3 comeback win.
The 21-year-old Kuznetsov, who is now at his top position in the rankings ever, was saddened by the result.
"I'm very disappointed. I thought I was ready to win and the opponent was within my powers." Kuznetsov said after the match.
"I didn't take my chances in the second set and in the third he started to play well, so it was difficult."
In round two, the 29-year-old Berlocq will face either world No. 65 Jerzy Janowicz of Poland or Germany's Benjamin Becker, ranked 76 in the world.
Earlier Tuesday, Igor Sijsling of the Netherlands ousted German qualifier Michael Berrer 7-6(7), 6-3, and Russia's Konstantin Kravchuk defeated Evgeny Korolev of Kazakhstan 6-4, 6-3 in a battle of two qualifiers.