Marat Safin continued his progress at his final home tournament, the St Petersburg Open, when his opponent Igor Andreev was forced to retire through injury.

The fifth-seeded Russian had lost the first set 6-3 but was 1-0 up in the second when a problem with his left knee caused him to withdraw.

Twenty-nine-year-old Safin, who bows out of professional tennis after next month's Masters event in Paris, will next face Denis Istomin in the quarter-finals.

The Uzbekistani player was the benefit of another retirement - this time top seed Mikhail Youzhny, who was 6-2 2-1 down when a back injury forced him out.

Ukrainian qualifier Sergiy Stakhovsky beat Andrey Kuznetsov 6-1 6-4, while Igor Kunitsyn beat fellow Russian Michail Elgin 6-2 6-3.