Nishikori, the No. 8 seed, took a 7-5, 6-4 decision from Berdych in a quarterfinal that took nearly 2 hours. He lost his serve once in each set but also managed two breaks in each set.
He heads into Saturday's semifinals against unseeded Marcos Baghdatis, who claimed a 6-2, 6-4 win over Dmitry Tursunov. Baghdatis had nine aces and won nearly three-quarters of the points on serve. He saved all three break-point chances Tursunov had.
Defending champion and No. 1 seed Andy Murray was pushed to three sets by seventh-seeded Stanislas Wawrinka before coming out a 6-2, 3-6, 6-2 winner. Murray saved six of the seven break points he faced but the one he didn't cost him the second set. He won the first and third sets with two breaks each, however.
Sixth-seeded Milos Raonic got by No. 3-seed Janko Tipsarevic 6-7 (5-7), 6-2, 7-6 (9-7) in a minor upset. Raonic had 24 aces -- and five double faults -- but didn't allow Tipsarevic a break point. Raonic is 2-0 versus Tipsarevic with the first meeting earlier this year going to tiebreakers in all three sets.
Murray and Raonic have split their previous meetings, both of which were this year. Baghdatis is 3-0 in his career against Nishikori.