Maria Sharapova's hopes of a second successive WTA Tour title ended on Saturday when she was upset 7-5, 6-2 by fellow Russian Elena Dementieva in the Los Angeles Open semi-finals.
The 19-year-old top seed, who won last week's Acura Classic in San Diego, lost a pulsating first set in just over an hour after battling back from 1-5 down.
Dementieva, in superb form from the baseline with her groundstrokes, then took advantage of a series of unforced errors by her opponent to sweep through the second set.
It was her second victory over Sharapova in seven career meetings and ended a run of eight wins in a row by the world number four.
"I feel really great," an elated Dementieva told reporters. "I have lost to her twice this year and I was really looking forward to this match because she is such a tough player.
"This win really means a lot to me.
"When you play against Maria, she is a great fighter and never gives up. That makes it difficult to play against her."
SAPPING HEAT
Asked whether she had been affected by the sapping heat at the Home Depot Center, the 24-year-old from Moscow replied: "It was tough to play but when you are on the court you are so focused you just want to win no matter what."
Third-seeded Dementieva, who had previously reached the semi-finals three times in Los Angeles without progressing further, will meet twice champion Serena Williams or Serbian Jelena Jankovic in Sunday's final.
American Williams, playing only her third event of the year because of a knee injury, was scheduled to take on 16th-seeded Jankovic in Saturday's second semi-final.
Sharapova, who had not dropped a set in her run of eight wins, felt she had paid the price for playing nine matches in 13 days.
"I haven't played this much in a while," she said after an erratic display of tennis featuring 46 unforced errors and eight double-faults.
"A year ago, I would probably haven't been able to play solid tennis for nine matches as I've been doing.
"I just felt a little flat today. I put two points together and would deflate for the next four. But I guess that's normal after playing so many matches in a row.
"But she made me work for it," added Sharapova, who was broken seven times by Dementieva and was forced to save six match points. "She played really well defensively."