Klizan ousted his Russian opponent 6-7 (11-13), 6-4, 7-6 in a match that took nearly 4 hours, and will face fourth-seeded Fabio Fognini of Italy in Sunday's championship match.
Fognini advanced with a 6-3, 6-4 win over Daniel Gimeno-Traver of Spain.
Saturday's loss derailed Youzhny's bid for a fourth trip to the St. Petersburg finals.
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