Defending champion Serena Williams reached the second round of Wimbledon with a 6-2 6-4 win over Switzerland's Amra Sadikovic.
Top-seeded American Williams served five double faults and only four aces in 73 minutes against the world number 148.
The six-time champion, 34, has now won 80 and lost 10 matches at Wimbledon.
"It wasn't tougher than I thought but it was definitely tough," she told BBC Sport.
"I never underestimate anyone. I started fast, and that's about it.
"This is me - I'm always shouting at myself, always pushing myself. It's absolutely nothing different.