Yani Tseng and Na Yeon Choi, the top two seeds, were both ousted Saturday morning at the Sybase Match Play Championship.
Tseng, a quarterfinal loser the last two years, dropped a 3 & 2 decision to Candie Kung.
Choi, who took third place last year, bogeyed the first extra hole to lose 1- down to Morgan Pressel.
Tseng and Kung had a tough battle in which each of the first 10 holes were won. Tseng took the first and fifth, but Kung won three in a row from the second at Hamilton Farm Golf Club.
Kung pushed her lead to 3-up with wins at six and seven, but Tseng fought back to take the eighth and ninth. Kung took the 10th to regain a 2-up cushion before the next two holes were halved with a bogey and a par.
Tseng parred the 13th to claim her last hole of the match. They halved 14 with pars. Kung birdied the 15th and 16th to close it out.
Choi and Pressel had a tight match in which neither player was more than 2-up. They traded wins on the first two holes with a pair of birdies. Choi parred the seventh and 10th to go 2-up.
Pressel birdied the 11th, but Choi responded with a birdie on No. 14 to again go 2-up. Pressel answered with birdies on 16 and 17 to square the match. They both parred the 18th before Choi tripped to a bogey on the first extra hole to drop the 1-down decision.
Kung will take on Julieta Granada, a 1-up winner over Karine Icher. Pressel will face Anna Nordqvist, a 3 & 1 victor against Amy Yang.
Stacy Lewis, the top remaining seed at No. 6, fended off Sun Young Yoo, 2-up, and moves on to play Azahara Munoz, a 2 & 1 winner over Jodi Ewart, who took out defending champion Suzann Pettersen and Sophie Gustafson early in the week.
Reigning U.S. Women's Open champion So Yeon Ryu will battle Vicky Hurst in the final match. Ryu downed Katherine Hull, 5 & 4, while Hurst held off 2010 runner-up Angela Stanford, 2&1.