Angelique Kerber smiling again after nightmare year as she marches on at Australian Open

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 against Su-Wei Hsieh’s 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 to secure a last-eight meeting with Madison Keys.

Having won the title in Sydney in her first tournament, Kerber is unbeaten this year. 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.”

Kerber 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.

World No 1 Simona Halep had too much experience for 20-year-old Naomi Osaka, beating the Japanese 6-3, 6-2.

In the men’s section, Roger Federer won in straight sets for the fourth round in a row, beating Hungary’s Marton Fucsovics 6-4, 7-6, 6-2 to reach his 14th Australian Open quarter-final and his 52nd in all Grand Slam events.

The Swiss, who is on course for a sixth Australian Open title, now faces Tomas Berdych, who beat Fabio Fognini 6-1, 6-4, 6-4.

Tennys Sandgren, a 26-year-old American making his debut here, sprang one of the surprises of the tournament when he beat the world No 5, Dominic Thiem.

Sandgren, the world No 97, won 6-2, 4-6, 7-6, 6-7, 6-3 after nearly four hours on court.