Del Potro, No. 4 in the world rankings and the tournament defending champion, fell to Ernests Gulbis 6-3, 6-4 and Marin Cilic later beat Murray, the second seed at No. 6 in the rankings, by the same score.
Gulbis, who lost to del Potro in Rotterdam last year in the second round, took 77 percent of the points on serve and allowed de Potro just one break opportunity. He was able to finish off a break in each set for the win.
Both Cilic and Murray won at least 70 percent of the points on serve but Cilic was 4-for-4 in saving Murray's break chances while cashing on three of his five.
Berdych, the only seeded player to reach the semifinals, dropped his serve just once while totaling four breaks. Berdych improved to 4-0 lifetime versus Janowicz but all three matches have gone three sets.
Sijsling only faced two breaks points and had a pair of break in each the first and third sets in improving to 3-0 in his career versus Kohlschreiber. They completed the match in a brisk 75 minutes.
Gulbis and Berdych are scheduled for Saturday's first semifinal. Berdych had won three of the five times they've met. Cilic is 2-0 all-time against Sijsling although both matches went three sets last year.