Angelique Kerber's bright start to 2018 continues as she reaches the last eight in Melbourne

The former world No 1 progressed to the quarter-finals of the Australian Open after being Su-Wei Hsieh on Monday

Kerber celebrates after securing victory against her Taiwan opponent (Getty)

The 2017 season could hardly have ended early enough for Angelique Kerber but the 30-year-old German has started the new campaign as if last year never happened. Having suffered two losses in the first round and two in the fourth in last year’s four Grand Slam tournaments, the former world No 1 has already gone one stage better in the first event of 2018 by reaching the quarter-finals here at the Australian Open.

There were times when Kerber struggled in the face of Su-Wei Hsieh’s bewitching mixture of unorthodox double-handed strokes and variations of pace and spin, but she held firm to beat the Taiwanese 4-6 7-5 6-2 and secure a last-eight meeting with Madison Keys.

Having won the title in Sydney in her first tournament, Kerber is unbeaten this year, having put her struggles of 2017 behind her. She appointed Wim Fissette as her coach at the end of last year after the Belgian parted company with Johanna Konta.

Following a superb 2016 campaign in which she won the Australian and US Opens, was runner-up at Wimbledon and became world No 1, Kerber ended 2017 at No 22 in the world rankings after failing to win another title.

“I’m just enjoying my tennis again,” Kerber said. “I think the most important thing for me when I'm on court is that I fight, that I play my game and enjoy it.”

Hsieh, who beat Garbine Muguruza, the Wimbledon champion, in the second round, frustrated Kerber with the ingenuity and unpredictability of her shots, but the German took charge after breaking serve at 5-5 in the second set.

Keys reached the quarter-finals with a crushing 6-3 6-2 victory over Caroline Garcia in just 68 minutes. The 22-year-old American, who was a semi-finalist here three years ago and a runner-up at last year’s US Open, has quickly found her form after ending her 2017 season early to rest a wrist problem.

Simona Halep, the world No 1, had too much experience for 20-year-old Naomi Osaka, beating the Japanese 6-3 6-2. Having been kept on court for nearly four hours by Lauren Davis in the previous round, the Romanian was grateful to win yesterday in just 79 minutes, given that she will face sixth-seed Karolina Pliskova after she beat her fellow Czech Barbora Strycova 6-7 (7-5), 6-3,6-2.