Serena Williams reaches fifth U.S. Open final , beating fifth seed Li Na . Chinese will play world No . 2 Williams in last year 's 's final . I think that 's what makes the difference . '' Azarenka defeats 83rd -ranked Flavia Pennetta in opening semifinal . She lost to Azarenka in last year 's title match at Flushing Meadows .
Serena Williams reaches fifth U.S. Open final , beating fifth seed Li Na . Chinese will play world No . 2 Williams in last year 's 's final . Azarenka defeats 83rd -ranked Flavia Pennetta in opening semifinal . She lost to Azarenka in last year 's title match at Flushing Meadows .