Tennis star Serena Williams battled back from a set down against compatriot Christina McHale to reach the quarter-finals of the Auckland Open. 

The 23-Grand-Slam-title winner won 3-6, 6-2, 6-3 in two hours with five aces and one double fault. 

The No 1 seed said in a post-match interview: "It was a good match for me, because I really need to play matches like that to get to my goals.

"Tournament time is super important and match time is good. It's fun to be out here after losing that first set, and I'm glad I'm still in the event.

"I got myself in a hole and I was able to get out of it, so that was satisfying."

Williams will face Laura Siegemund from Germany in the quarter-finals tomorrow. 

She has also seen success in the doubles with partner Caroline Wozniacki. The duo stormed into the semi-finals after they beat No 1 seeds Caroline Dolehide and Johanna Larsson.

Elsewhere in the tournament, Siegemund ended Coco Gauff's chances of reaching the quarter-finals after she won 5-7, 6-2, 6-3.

The German, currently ranked world No 73, struck 27 winners and broke 15-year-old Gauff, eight times. 

Seed No 5 Wozniacki has also been successful in the singles after defeating the USA's Lauren Davis 6-1, 4-6, 6-4. 

Wozniacki, 29, who is set to retire after the Australian Open eliminated the 2017 champion in just over two hours. 

The first set saw the Dane dominate as she denied Davis a chance, but the American found her swing and produced several winners in the second set, forcing a set decider. But Wozniacki held her form in the final set to seal victory.

She is set to face fourth seed Julia Goerges in the quarter-finals tomorrow afternoon.