Serena toils to scrappy opening victory

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 28/6/16 USA's Serena Williams celebrates during her match against Switzerland's Amra Sadikovic REUTERS/Stefan Wermuth

LONDON (Reuters) - Defending champion Serena Williams stuttered to a low-key and error-strewn 6-2 6-4 first-round victory over Swiss qualifier Amra Sadikovic on Tuesday.

Looking ill-at-ease, as though her quest for an elusive 22nd grand slam title was weighing heavily on her shoulders, Williams struggled with her serve and sprayed balls wide on both sides of the court. She served three double faults in the fifth game of the first set.