US Open champion Sloane Stephens was unable to make the transition from clay to grass as she crashed out in the first round of Wimbledon with a straight-sets defeat to Donna Vekic.
Runner-up at the French Open last month, Stephens was downed 6-1 6-3 by the unseeded Croat.
“Today just wasn’t my day,” Stephens said.
“I wish I could have played better. I wish I would have made some more balls. I wish I could have pushed her a little bit more. It just wasn’t working.
She said she had found the switch from Paris to London difficult.
“The balls from clay to grass are completely different,” the fourth seed.
“The ball stays very low here. You have to make a little bit more of an adjustment. Everyone is dealing with the same conditions, so it’s not just me.”
It was a tough draw as Vekic is a threat on grass but Stephens put in an erratic display.
“I am very happy to win today, it was a tough match,” Vekic said. “I am really happy.
“I tried to go out there and be aggressive, I was struggling with my serve, it was windy, so I am happy to get through.
“I played all the tournaments on grass, I really enjoy playing on it and it
helped me.”
Australian Open champion Caroline Wozniacki safely navigated her way past Varvara Lepchenko.
The Danish second seed was second on Centre Court, just 48 hours after the title in Eastbourne.
She had little trouble getting past the American, winning 6-0 6-3.
Six-time champion Venus Williams also overcame a scare to beat Swede Johanna Larsson.
Williams came back from a set down to win 6-7 (3-7) 6-2 6-1.
Karolina Pliskova also had a battle on her hands to get past British hopeful Harriet Dart.
The Czech, who will be eyeing her maiden grand slam success at SW19, needed three sets, triumphing 7-6 (7-2) 2-6 6-1.
Magdalena Rybarikova became the first seed to lose as she was beaten 7-5 6-3 by Sorana Cirstea while 22nd seed Anastasija Sevastova was ousted 6-1 2-6 6-4 by Italian Camila Giorgi.
Former No.1 Victoria Azarenka came through in straight sets against Ekaterina Alexandrova while 2015 quarter-finalist Madison Keys, the 10th seed, eased past Ajla Tomljanovic 6-4 6-2 in 62 minutes.