MADRID, Spain - Vania King and Yaroslava Shvedova are having their best tournament of the three they've played this year, but it was far from a smooth path into the Mutua Madrid Open doubles semifinals on Thursday.

The third-seeded King and Shvedova, whose other results this year consisted of a quarterfinal appearance in Indian Wells and a first round loss in Miami, took on sixth-seeded Bethanie Mattek-Sands and Meghann Shaughnessy, who came into the quarterfinal clash with an 18-5 record in 2011. In their 75 57 108 triumph, King and Shvedova let a 5-3 second set lead slip away, including a match point at 5-4, deuce on Shvedova's serve. They also trailed, 6-3, in the match tie-break and were two points from defeat at 8-7 before winning the showdown's final three points. In Friday's semifinals, they will take on fifth-seeded Victoria Azarenka and Maria Kirilenko.

There was another wild quarterfinal on Thursday, with Casey Dellacqua and Rennae Stubbs surviving Hsieh Su-Wei and Yan Zi, 46 76(5) 119. The Australians trailed, 64 30, were down 5-3 in the second set tie-break and had a match point against them at 9-8 in the match tie-break before rallying each time. Dellacqua and Stubbs had only played one previous match together before Madrid, losing in the first round of Birmingham in 2008.

Next up for Dellacqua and Stubbs are No.2 seeds Kveta Peschke and Katarina Srebotnik, who snapped Sania Mirza and Elena Vesnina's six match winning streak, 75 75. After a brief lull in which they lost their openers at Indian Wells and Miami, Peschke and Srebotnik have now won four of their last five matches to improve their record this year to 22-6.