MEMPHIS (Tennessee) (AFP) Eighth-seeded Sam Querrey upset top-seeded Andy Roddick 7-5, 3-6, 6-1 to book a semi-final berth Friday as top seed Maria Sharapova moved into the womens final at this combined ATP/WTA tennis tournament. Querrey, who lost to Roddick in the San Jose semi-finals last week despite never facing a break point, poured it on in the third set to notch his best result in Memphis. Roddicks double-fault in the second game of the third set gave Querrey the upper hand, and Querrey made the most of it. Youre not going to get that too many times from Andy, but Ill take it, said Querrey. When that rare opportunity comes, youve just got to take advantage of it. I thought I did a good job there, and just kept the momentum going and played an unbelievable third set. It was disappointing, said Roddick. Today I played one sloppy game in the third set and that was it. Sometimes at this level theres not much in between it. With the victory Americas Querrey improved on his quarter-final finishes here in 2007 and 2009. In the semi-finals hell take on 21-year-old Latvian Ernests Gulbis, who rallied for a 3-6, 6-3, 7-6 (7/3) victory over fifth-seeded Czech Tomas Berdych. Gulbis trailed 4-1 in the final set when he received treatment on his left knee, then rallied for the victory. He said the patella tendinitis that bothered him was a long-term problem. Ive been dealing with for more than one-and-a-half years, Gulbis said, adding that the trainer who worked on him knew exactly what to do. Sixth-seeded American John Isner downed Croatian Ivo Karlovic 6-1, 7-6 (9/7) to book a semi-final clash with German Philipp Petzschner, a 6-1, 1-6, 6-1 winner over Slovakian Lukas Lacko. Russias Sharapova advanced to the final in cue with a 6-4, 6-3 victory over fifth-seeded Czech Petra Kvitova. Shell face Swedens Sofia Arvidsson, a 6-4, 4-6, 6-4 winner over Britains Anne Keothavong.