Marat Safin, playing in his penultimate tournament before retiring, beat Denis Istomin 6-0 7-6 to reach the St Petersburg Tennis Open semi-finals.
Safin raced through the first set in less than 25 minutes and took a 2-0 lead in the second before the 101st-ranked Uzbek put up more of a fight.
The 29-year-old Russian, who will end his tennis career at next month's Paris Masters, served for the match at 5-4, but Istomin broke back and forced a tie-breaker two games later.
The former world number one finally sealed victory with his 12th ace and will take on Ukrainian qualifier Sergiy Stakhovsky in the semi-finals.
The World number 93 Stakhovsky beat Germany's Bjoern Phau 6-2 7-5 in the earlier match at the St Petersburg's Sports Complex.