Usually sunny Kim Clijsters smashed a racket in a moment of first set frustration on Friday before settling down to a straight-set win over Martina Hingis and a semi-final berth in this US$1.34 million WTA tournament.
The sweet-faced Belgian top seed let her emotions rip after Hingis broke back for 4-all in the first set, but channelled her frustrations into a 7-5, 6-2 victory over the eighth-seeded Swiss.
And once she had extended her quarter-final dominance over Hingis this year, who returned to the game in January after three years away, Clijsters managed to explain away the out-of-character episode.
Clijsters has now beaten Hingis three times this year -- all at the quarter-finals stage -- in Melbourne, Paris and San Diego.
Second-seeded Russian Maria Sharapova mowed down defending champion Mary Pierce 6-2, 6-3, winning six consecutive games en route to a semi-final clash with Patty Schnyder.
Sharapova needed just 58 minutes to book her meeting with Schnyder, who reached her second semi-final in as many weeks with a 6-4, 6-3 victory over Elena Dementieva.
Schnyder, runner-up last weekend at Stanford to Clijsters, pounced on more than 40 unforced errors from Dementieva, one of three Russians who reached the last eight.
Former champion Lleyton Hewitt was upset by France's Arnaud Clement 7-6 (1), 6-4 in the quarter-final of the Legg Mason Classic on Friday. With 11 aces, Clement earned his first victory over third-seeded Hewitt in eight matches since 1999.
"We've played a couple of tough matches, but he was always a little better at the important moments," Clement said. "Today was different."
Typical of their clashes, it took 2 hours, 10 minutes to separate Hewitt, the 2004 Washington winner, and Clement, who reached his first tour semi-finals since February at Marseille, where he won his third career title.
Clement will face Marat Safin, who followed up his defeat of top-seeded James Blake by outlasting South Africa's Wesley Moodie 7-6 (5), 7-6 (9) in just under 2 hours.
The Russian reached his first semi-finals since April at Valenica. The former world No. 1 has slumped to No. 92 since he returned to the tour in February from a knee injury which had sidelined him from August.
Countryman Dmitry Tursunov dispatched 2003 champ Tim Henman 6-3, 6-2 without offering the British veteran a break chance.
Seventh-seeded Tursunov was runner-up in Los Angeles last week and was sure to improve his career-high 29th ranking with a semi-final against British No. 1 Andy Murray.
Murray struggled to put away Mardy Fish of the US 6-2, 6-4.