Sofia Kenin lost against Garbine Muguruza 2-6, 2-6.

MELBOURNE (AFP) – A teary-eyed Australian Open champion Sofia Kenin lost a repeat of last year’s final against Garbine Muguruza as warm-up tournaments for the Grand Slam resumed Friday after the latest coronavirus scare.

World number one Ashleigh Barty ground out a tough win over Shelby Rogers but fourth-ranked Kenin flamed out of the Yarra Valley Classic with a straight-sets thrashing by Muguruza.

Six build-up tournaments for next week’s Australian Open have returned to action after a coronavirus case at a designated tournament hotel halted play Thursday and forced hundreds of players and officials into isolation.

Storms forecast for Friday threatened to increase the backlog, but to ease the congestion WTA clashes were reduced to two sets and a 10-point super tiebreaker instead of the traditional three sets.

World number 15 Muguruza has been in aggressive form in Melbourne, dropping just four games in two matches prior, and impressively hit the lines to run Kenin ragged 6-2, 6-2.

"It’s always better to know that you’ve played well here... and this is definitely the Happy Slam," said the Spaniard, using the Australian Open’s nickname.

The two-time Grand Slam champion is showing the form that saw her rise to the top of the rankings in 2017 but it’s a different story for defending Australian Open champion Kenin.

The 22-year-old’s return to the scene of her stunning breakthrough last year has been rocky, after playing just one set in her opener against Camila Giorgi and then surviving a three-set scare against fellow American Jessica Pegula.

Her struggles continued with 28 unforced errors as the flummoxed American departed in tears.

Earlier Barty, who has yet to rediscover her best after a long layoff, prevailed 7-5, 2-6, 10-4 in 92 minutes to reach the Yarra Valley Classic semi-finals.

"I thought I did well to hang in there," she said. "There were some challenges but happy to click into gear and find a way."

The 24-year-old Barty, competing in her first tournament in 11 months, appeared fresh after Thursday’s unexpected stoppage having played two singles matches within 20 hours earlier in the week.

Barty, playing with the roof shut on Margaret Court Arena, overcame a second-set stutter with a ruthless performance in the super tiebreaker.

Barty, hoping to break her country’s 43-year singles title drought at the Australian Open, is on course for a blockbuster contest with 23-time Grand Slam champion Serena Williams, who will be in action later Friday against fellow American Danielle Collins.

Two-time Australian Open champion Victoria Azarenka saved two match points to beat Yulia Putintseva 6-4, 1-6, 11-9 and move into the quarter-finals of the Grampians Trophy in her season debut.

Naomi Osaka and Simona Halep also play later.