Dubai - Holder Belinda Bencic ran off the first 19 points against Anastasia Pavlyuchenkova before collapsing to a 1-6, 6-1, 6-1 loss on Tuesday at the Dubai Championships.
Another former champion, the 2017 and 2018 winner Elina Svitolina, also fell, 6-2, 6-1, to US qualifier Jennifer Brady.
Pavlyuchenkova could not have made a worse start.
"It's tennis, sometimes it happens," the 31st-ranked Russian said "You go out there and you just don't feel anything.
"I just kept on fighting, still trying to hit every ball, trying to be there
"It doesn't matter what the score is, just play. Slowly I started to turn it around, I started to find my game."
"I honestly wasn't focusing on the score. Sometimes you can play amazing tennis and still lose 6-1. In the third set, it was a good level from both of us."
Pavlyuchenkova advanced in 92 minutes.
Bencic, who is Swiss was seeded four and Ukrainian Svitolina third. That leaves the spotlight to tournament No 1 Simona Halep and second-seeded Karolina Pliskova, who begin in the second round after byes.
Weekend ATP Rotterdam winner Gael Monfils watched in pain as girlfriend Svitolina went down to Brady.
Svitolina had little to offer as the 52nd-ranked Brady gained her second victory this season over a Top 10 opponent after beating Ashleigh Barty in Brisbane.
The Ukrainian's usually steady game was nowhere to be found at the Aviation Club as first-round play concluded.
"It was not a bad start, but then everything just went downhill," Svitolina said.
"I wish I could regroup better. In the end, I didn't feel so good the ball. Just everything was all over the place today.
"At this level it's tough to pick just one thing: everybody is putting the ball over the net, and you have to play long rallies, you have to build the points.
"Before I was more composed with my game. Now it's little bit of a struggle. Maybe mentally or something."
Brady, a qualifier with three matches already here, said that her own attitude as underdog may have helped.
"I'm respecting my opponent, but not to the point where I put her on a pedestal.
"I was just focused on my game plan, myself, I competed well from the very beginning.
"From the start, maybe she felt my presence. I was happy with the way I performed."
Brady's win paved the way for fellow American and Australian Open winner Sofia Kenin, who will later begin her campaign against Elena Rybakina, winner of Hobart in January and runner-up at the weekend in St Petersburg.
Frenchwoman Kristina Mladenovic beat fellow qualifier Aliaksandra Sasnovich 6-4, 6-3 to set up a second-round date with Pliskova.