MASON, Ohio (AP) -- Venus Williams' reinvigorating week ended with a gritty comeback that wasn't quite enough.
Williams played through a bad back that forced her to get treatment and reduced her serve to 63 mph before finally fading in the third set. China's Li Na reached the final of the Western & Southern Open with a 7-5, 3-6, 6-1 victory Saturday night.
Li is trying for her first title this season. She lost in finals at Sydney, Rome and Montreal, where Petra Kvitova beat her a week ago.
Kvitova played Angelique Kerber in the other semifinal. Kerber ended Serena Williams' 19-match winning streak a day earlier.
Serena watched from the stands while her older sister struggled, showing the strain of a week capped by her fourth grueling, full-set match.