Defending champion Simona Halep was on sensational form against CoCo Vandeweghe, booking herself the first semifinal slot at the Mutua Madrid Open.

Defending champion Simona Halep was on sensational form against CoCo Vandeweghe, booking herself the first semifinal slot at the Mutua Madrid Open as she crushed the American, 6-1, 6-1.

"It was very good match actually," Halep said in her post-match press conference. "I knew what I have to do against her. I knew that I have to play fast, to make her move, to hit from distance.

"I tried also to be more aggressive from her second serve. I served pretty well. I don't believe I lost a serve today!"

She wrapped up the straight-sets win in under an hour - which included time off court for a rain delay.

"I was a little bit nervous, to be honest, before the match, because she has a big serve. It's always tough to play with someone who has a big serve."

The Romanian was in no mood to waste time from the off, making the early break to assert herself in the first set, and then consolidating on it. 

"I didn't expect to be so fast today. But I was focused. I was concentrated for every point. I knew that it's going to be important. Also when the rain came, I tried to just play fast, to stay there in the match.

"I think I did pretty well today. I'm really happy with the way also I played, and with my attitude."

The 25-year-old American could find no response, and the tournament's No.3 seed employed much the same tactic in the second set, with equal success.

"I feel different, but not just this week," Halep admitted. "In the last five weeks, I feel different. It's much better. I keep more energy in this way. When I finish a match like yesterday, where it was really tough, I didn't feel tired. That makes me stronger and makes me to understand.

"It puts me in the way to understand that it's much better to stay relaxed, just calm, not talking and doing other stuff on court."

Halep will next face Anastasija Sevastova, who reached her first career Premier Mandatory semifinal after beating Kiki Bertens, for a place in the final.

"Every time I say the same thing: Every match is different. I don't expect to be easy like in Stuttgart. I don't expect anything. So I just want to go there. I know that I have my chance to win the match. I know what I have to play.

"Hopefully I will feel my game and just doing my best to win the match. I really wish to be in the final again here."