Serena Williams has extended her presumptive farewell tour by at least two more days.
The 23-time major singles champion overcame early nerves and a misfiring serve to win 6-3, 6-3 against Danka Kovinic in their US Open first-round match at Arthur Ashe Stadium, launching what is expected to be the final tournament of her glittering 27-year professional career on a winning note.