Ekaterina Makarova described Serena Williams' US Open semi-final performance on Friday as "unbelievable".
The American world number one was dominant and showed why she is fancied to win her 18th grand slam title, crushing Makarova 6-1 6-3 in an hour.
Williams hit 24 winners in a typically aggressive display, setting up a clash in the final against Caroline Wozniacki.
Makarova said Williams, who she beat at the 2012 Australian Open, was simply too good at Flushing Meadows.
"Against Serena always you need to play aggressive more than she is," the Russian said.
"But she's doing it so well and she's hitting so early the ball, so it's always tough to be more aggressive than she is.
"I was trying to make long point. I was trying to let her move, but she was unbelievable today. She was moving well and playing unbelievable angles."
Makarova said she was surprised by Williams' aggression but was pleased with her showing after reaching her maiden grand slam semi-final.
"She's a great, unbelievable player. It's always tough to play against her. Today she was so aggressive," Makarova said.
"Maybe I didn't think that she will be that aggressive. Like she's just coming, you know, so early, so sometimes I was too late because she was too fast.
"I'm still so happy that I was in semis."