World number one Dinara Safina demolished the previously in-form Flavia Pennetta for the loss of just two games to make the Cincinnati final.
The Russian won 6-2 6-0 in just 56 minutes to bring an end to Pennetta's 15-match unbeaten run that had included titles in Palermo and Los Angeles.
The Italian had blisters on her feet and played with her right ankle taped.
Safina will face fifth seed Jelena Jankovic in the final after the Serbian beat Elena Dementieva.
Jankovic had a very different route to the final, with a topsy-turvy 7-6 (7-2) 0-6 7-6 (8-6) victory in a match that saw 13 breaks of serve and 25 double faults.
"I can't believe I won this match," said Jankovic, who was 6-2 down in the third-set tie-break before winning six points in a row to clinch the victory.
"Every match I feel better," said Safina. "Today, stepping on the court, I was feeling very good and confident. I was feeling very good stepping in."
Pennetta said: "She was playing much better than me. I was a little bit tired, of course, but I didn't lose for that. She was playing unbelievable."