World No 1 Karolina Pliskova admitted she is struggling to cope with the pressure after surviving a major scare in the second round of the US Open.
The Czech top seed lost the first set to American Nicole Gibbs but recovered to win 2-6, 6-3, 6-4.
Pliskova has had a stellar 12 months, which began when she reached the final here, and she climbed to the top of the rankings after Wimbledon.
Karolina Pliskova beat Nicole Gibbs to win 2-6, 6-3, 6-4 in the US Open second round
The 25-year-old said: 'I think you cannot really see how I'm feeling inside. Even when I was playing some matches last year, two years before, I still have some nerves in myself.
'But I think now it's even more. Every match, I have to win. There is enough pressure on me. They're outsiders, so they're always going to play well against me.'
Asked how the pressure affected her game, Pliskova said: 'My legs, I felt a little bit slower in the first set. And my hands, as well. Then it's tough to play like this. I have an aggressive game, so maybe if someone is defending it