As if McLaren's woes with their car were not enough to contend with, the 33-year-old will start a miserable 14th on the back of tyre pressures being incorrectly set for his run in the second qualifying session.
By contrast, team-mate Sergio Perez comfortably made it into the top 10, finishing 0.565secs ahead of Button, whose previous worst display was in last year's British Grand Prix when he lined up 16th.
It means for the first time this season since he switched to McLaren, Perez starts ahead of Button as he ultimately finished ninth in the top-10 shoot-out at Barcelona's Circuit de Catalunya.
"A lot of new parts are on the car and they've made a little bit of a difference, but not really enough to challenge at the front, although it's good to see they are making progress," said Button.
"In Q1 the car didn't feel too bad, and then in Q2 I didn't have the grip on my last run. The (tyre) pressures came in massively high.
"I was surprised to see Sergio was still out there fighting compared to what I had out there in terms of balance and pace. He did a good job and obviously did everything right.
"In the race we should be a little better compared to some of our competitors, but we have a lot of competitors these days, that's the problem.
"Our race pace is okay, but it's not much better than our qualifying pace, so it's going to be a tricky afternoon, but we will hopefully make the best of it and get some points."
Under-pressure team principal Martin Whitmarsh was at least relieved to see Perez in the top 10 for the second time this year.
"In Q2 Checo did a fantastic job. It was a really good run," said Whitmarsh.
"We could have been tactical in Q3 and kept some new tyres for the race, but I think he was driving so well we thought 'let's go for it'.
"In Q3, he was two tenths (of a second) up, but lost time at end of the lap.
"Despite that, given our car isn't quick enough, you've got to applaud him.
"As for Jenson, it was a disappointing outcome. We've not analysed the data yet, but there is some evidence the tyre pressures were too high otherwise we hope he would have snuck through.
"We've been working hard and will keep working hard."
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