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Russia's Maria Sharapova scored a routine 6-4, 6-2 victory Saturday over world No. 1 Victoria Azarenka to reach the final of the WTA Tour Championships in Istanbul, where she will square off against American Serena Williams.

The second-ranked Sharapova kept her unforced errors to a minimum against the Belarusian, who appeared to lack freshness after a long season that saw her finish the year No. 1 for the first time.

The Russian took the match in one hour and 36 minutes, exacting some revenge on an opponent who had defeated her in seven of their 11 matches prior to Saturday, including this year's Australian Open final and the U.S. Open semifinals.

Her match-up problems against Azarenka, however, pale in comparison to her struggles against Williams, who has won nine of their 11 matches and eight matches in a row.

The last three matches between them have been particularly lopsided, with Sharapova winning just nine games.

But Sharapova's two wins over Serena were big ones: the 2004 Wimbledon final and that year's WTA Tour Championships final.

Williams advanced to Sunday's final by steamrolling Poland's Agnieszka Radwanska 6-2, 6-1.

Radwanska, who also lost to Serena in this year's Wimbledon final, was battling fatigue after defeating Italy's Sara Errani 6-7 (8-10), 7-5, 6-4 on Friday in three-and-a-half hours, the longest three-set contest in the tournament's history.

The tournament's defending champion, Czech Petra Kvitova, withdrew from the tournament due to a viral infection after losing her first match to Radwanska in straight sets. EFE