ROTTERDAM - Top seed Juan Martin del Potro and number two Andy Murray were both knocked out of the Rotterdam World Tennis in quarter-final upsets on Friday by the same 6-3, 6-4 scorelines. Latvian Ernests Gulbis ended del Potro's winning run when he beat the top seed, while unseeded Croatian Marin Cilic won his eighth match in a row this season with Murray his latest victim.The Scot had claimed victory in nine of their 10 previous matches but was well off his game as he went out in 71 minutes, losing serve once in each set. "I would have liked to have done better but I'm not frustrated. I'm striking the ball well," said Murray, who now has 10 days before his next start in Acapulco.Third seed Tomas Berdych maintained the seeded status quo with his 6-7 (9/11), 6-2, 6-4 comeback over Poland's Jerzy Janowicz taking nearly two-and-a-half hours. Dutchman Igor Sijsling beat German Philipp Kohlschreiber 6-2, 2-6, 6-1 to become the first home player to reach the last four here in more than a decade. He will face Cilic, champion last week at home in Zagreb. Gulbis, who can be brilliant or less than impressive depending on his mood, preyed upon Del Potro as the Argentine took treatment before the start of the second set on the left wrist which has been posing problems since last month in Australia.Del Potro came to the match without the ability to hit a penetrating backhand as he plays with medical permission while trying to clear up his wrist problem. Gulbis will be playing in his first semi-final at the event after advancing in 81 minutes with a dozen aces as he forced Del Potro to save seven of nine break points. "If you let him play, he will play," Gulbis said. "I don't give any timing, I made him play bad. I concentrated on his backhand, we had a lot of long rallies. I played well at the right moments. I felt in control almost all the match, I was nervous in the last game but a good kind of nervous, I kept on playing well. Those are the kinds of nerves that I can handle." Del Potro said he has felt delicate all week but still believes his dodgy wrist is on the mend. "My doctor is confident and I will keep on playing tournaments as long as the wrist does not get worse," said the ATP number four. "It's getting better very slowly but it can be tough to remain optimistic all the time. When you are not at 100 per cent you are thinking about your problems instead of your tennis. That's what happening this week. He played a good match and deserved to win. He played a smart strategy against my backhand." Murray is still recovering fitness after autumn back surgery and has not looked comfortable all week. "He served well and played a good match. I created opportunites but could not convert them. he took his chances and I didn't make enough returns. "I would have liked to have done better but I'm not frustrated. I'm striking the ball well." Cilic said his big serve saw him through. "Tonight was a good win, I played some great tennis," said the Croatian. "I felt I was serving very well, it got me out of trouble, especially in the second set (when he saved three break points to take a 4-2 lead). Andy was struggling a bit and I was able to take advantage of the situation in a good way." There are days like that, I'm just happy for me. It's my first semi-final here and I hope to take it farther."