Angelique Kerber was one of at least seven seeds who crashed out of the Qatar Open on Tuesday, in the German's first singles tournament since winning her first Grand Slam title in Melbourne last month.
The Australian Open champion lost her second round match -- she received a first round bye -- in straight sets 7-5, 6-1 to China's Zheng Saisai, who is ranked 70 places below the world number two.
And on a disastrous day in Doha for the top players, Kerber was joined by the number two seed Simona Halep, who lost in three sets to Elena Vesnina.
Also out was defending champion and number seven seed Lucie Safarova. She was defeated in straight sets by Turkey's Cagla Buyukakcay.
Adding to the carnage, the number six seed Belinda Bencic, number 12 seed Svetlana Kuznetsova, number 14 seed Jelena Jankovic and the number 16 seed Sara Errani also perished.
But on an extraordinary day, it was Kerber's defeat which proved the most shocking.
In a lacklustre and timid performance, the German lost her serve six times, hit 38 unforced errors -- Saisai hit only eight -- and was beaten in just one hour and eighteen minutes as her opponent dominated.
The second set took just 28 minutes as Kerber's game collapsed.
The out-of-sorts Kerber, who has not played any singles tournaments since beating Serena Williams in Melbourne on January 30, grew increasingly exasperated with her form on a blustery night in Doha and at one point could be heard telling her coach Torben Beltz that she was tired and had no energy.
Afterwards, the Poland-based German said she did not know if her poor performance was down to a lack of match fitness or not being able to respond to the new pressure of being a Grand Slam champion.
"I don't know if it was the pressure or not. I know, of course, pressures from the last years, but maybe it was both," she told reporters.
"I mean, I was feeling this morning also not good when I was practising. This is actually what I can say, I don't know how many mistakes I did today. This is not my game, to make so many mistakes.
"I was trying to go for it. I think it was more like I was not feeling my game and not finding my rhythm."
A delighted Saisai plays Canada's Eugenie Bouchard in the third round.
Bouchard beat the Czech Republic's Denisa Allertova 7-6 (7-0), 7-5 as she continues her recovery from a traumatic end to 2015.
The unseeded Bouchard, who confirmed she is still pursuing legal action against the United States Tennis Association after she slipped and fell in a locker room during the US Open last September, said she was just happy to be playing tennis again.
"I can't complain even if I play terrible, I'm so happy to be back on tour," she said.
Halep, the 2014 Qatar Open champion, lost in three sets to Vesnina, despite taking the first on a tie-break and leading 4-1 in the second.
But she eventually fell 7-6 (7-1), 4-6, 1-6.
"(I'm) a bit disappointed that I lost from a set and 4-1, but that's tennis," said the Romanian afterwards, who delayed nose surgery to play in Qatar.
The 2015 champion Safarova, who was returning from injury, went down 6-7, 5-7 to Buyukakcay.
It all means that the top player remaining is the number three seed Agnieszka Radwanska who won 6-4, 6-4 against Kateryna Bondarenko from Ukraine.
"Obviously it was hard conditions, but I won," said Radwanska afterwards. "That's the most important thing."
Also through is number five seed Petra Kvitova who won 7-6 (7-2), 6-4 against Czech compatriot Barbora Strycova