Serena Williams did a quick little dance behind the baseline to remind herself to move her feet. Top-ranked Williams’ first competitive match of the season, on New Year’s Eve, was by no means perfect, but the 6-4, 6-4 win over Andrea Petkovic at the Brisbane International was a decent start against a player who has been ranked as high as No. 9. Williams made 36 unforced errors, including the big miss on Petkovic’s floater in the fifth game of the second set, but hit 35 winners and fired 11 aces including one at 122 mph to bring up set point in the first. Williams started 2013 in Brisbane with a title, the first of 11 for a year that included two major championships.