Second-ranked Victoria Azarenka overcame an erratic performance to beat an ailing Sara Errani 7-6 (7-4) 6-2 in the opening match of the WTA Championships on Tuesday.

Errani hurt her right calf in the third game of the second set and took a medical timeout to have it treated.

Several times after that she seemed to be bothered by the injury and to favour her right leg, although she returned after the medical timeout to break Azarenka’s serve to level at 2-2. She did not win another game though.

Errani served for the set three times – and dropped serve each time as both players produced sloppy play with little rhythm.

Azarenka managed to hold her serve only once through the first eight games but seized her chance when it came.

She won four straight points in the tiebreaker to take a 5-3 lead, then faltered when she served her sixth double-fault.

But an error by Errani gave Azarenka two set points. Errani then committed a double-fault and Azarenka had the set.

Azerenka, who was runner-up in the event in 2011 and a semi-finalist last year, finished with eight double-faults but she also had 51 winners for Errani’s 28.

Azarenka’s win was her first since losing the US Open final to Serena Williams, who was next on court against Angelique Kerber.

Azarenka lost both of her opening matches in Tokyo and Beijing, where she had 15 double-faults.

The tournament brings together the top eight players in the world. Third-ranked Maria Sharapova dropped out with a shoulder injury.