ST. PETERSBURG, Russia — Marat Safin advanced to his first semifinal in 23 events Friday, beating Denis Istomin of Uzbekistan 6-0, 7-6 (4) at the St. Petersburg Open.

The two-time champion from Russian, currently ranked 77th, last played in the semifinals at the Kremlin Cup a year ago.

Safin won eight straight games to lead 2-0 in the second set, but Istomin broke back in the sixth game to make it 3-3. Safin broke again for a 5-4 lead with a precise crosscourt return, but was sloppy while serving for the match and sent it to a tiebreaker.

Istomin netted a backhand slice on a match point.

Safin, a two-time Grand Slam champion, is playing his last season on the ATP tour. The former No. 1 has won 15 career titles, his last at the 2005 Australian Open. He had reached two previous quarterfinals this season but gone no further.

The Russian will play Ukrainian qualifier Sergiy Stakhovsky, who beat German veteran Bjorn Phau 6-2, 7-5, for a chance at the finals.

Earlier, eight-seeded Horacio Zeballos of Argentina reached his first career ATP tour semifinal by beating Ernests Gulbis of Latvia 7-6 (8), 6-4.

Playing in his only fourth ATP event, the 54th-ranked Zeballos broke his opponent in the third game of the second set and served a winner to close the match.

The 93rd-ranked Stakhovsky broke three times in the first set and once in the second set to reach his second career semifinal.

Second-seeded Victor Hanescu of Romania played Igor Kunitsyn of Russia later Friday.