Beaten Andy Murray was at a loss to explain his Indian Wells woes after a shock second-round defeat against Canada's Vasek Pospisil.
The Scot's best showing in California came in 2009 as a runner-up to Rafael Nadal and this 6-4 7-6 (7/5) defeat was his first in five meetings against the world number 129.
As such, Indian Wells and Monte Carlo remain the two ATP Tour 1000 events to elude him.
"I don't know exactly why it is, because in practice I normally play pretty well," he said of his struggles in California.
Speaking at his post-match press conference he added: "Some years I've played well. Some years it just hasn't quite happened for me.
"I don't know exactly why that is. I don't know if it's the conditions. I really don't know why I haven't played my best here over the years."
Murray, who claimed his maiden title of 2017 at the Dubai Duty Free Championships last week, was sluggish from the start in the BNP Paribas Open clash.
The 29-year-old was broken four times in total by Pospisil, who celebrated his biggest-ever win on the ATP Tour and declared it as his finest hour.
"He's always played that way, maybe he was doing it better this evening," Murray said of an opponent who needed an hour and 50 minutes to beat him.
"He was maybe a bit more solid from the back, a bit more consistent from the back of the court.
"That allows you and gives you more opportunities to come to the net. If you're making mistakes in the first three, four shots of the rally, it's not easy to come in on the correct ball.
"When you're a little bit more solid, you can be patient and wait for the right shot to come in on."
In a sign of things to come, Murray was forced to save three break points just to hold his first service game but broke the Canadian in the fourth to lead 3-1.
The Scot saved another break point in the fifth but Pospisil dug deep and eventually converted his fifth opportunity on the Murray serve.
In a topsy-turvy first set Murray then hit straight back before Pospisil, a Wimbledon quarter-finalist in 2015, broke once more.
Pospisil pulled off a wonderful return to clinch his third break point in the ninth game and held his nerve to serve out the first set.
Pospisil earned a slice of luck to clinch yet another break in the first game of the second set before holding to leave Murray stunned.
The reigning Wimbledon champion was on the ropes once more in the third game of the second but rallied to secure a foothold in the clash.
Murray and Pospisil exchanged service games until the tie-break but it did not prove to be a turning point for the Brit.
Pospisil won three straight points for a 3-1 lead and entered the change of ends 4-2 in front, much to the delight of the Californian crowd.
With four match points to play with, the Canadian converted the fourth to secure a place in round three at the expense of the top seed.
"It's an amazing feeling," said Pospisil. "Obviously, it happened pretty quick. I feel like on a comeback trail. I had a tough year last year for many, many different reasons.
"I feel the last couple months I really found my hunger and my motivation to be back on the court training hard again.
"I felt like a big result was coming, because I believe in my abilities, but just kind of had to put the pieces together again.
"Obviously to beat the number one player in the world is incredible. I mean, it's the biggest win of my career, and I'm just thrilled right now."
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