Tech 3 Yamaha rider Zarco was forced into the first part of qualifying after setting the 15th fastest time in the third practice session on Saturday morning.
The Frenchman then missed a place in Q2 by almost a tenth of a second and was fourth behind Andrea Dovizioso, Takaaki Nakagami and Aleix Espargaro in Q1.
A six-place penalty for Espargaro lifts Zarco to 13th on the grid, but it’s his worst starting position since last year’s German Grand Prix.
“Overall, it was a difficult Saturday,” said Zarco discouraged. “Yesterday I was pretty happy and today I don’t understand why we can’t improve and do better.
“It’s really hard to accept. I’ve tried my best, I’ve tried to improve where I’m weak. I’ve tried to understand where I need to be better and what I can ask of the team that we have not found.”
“So it makes me sad and it does [puts] me in a difficult situation to start tomorrow’s race and set a good goal.
“In order to achieve a good race pace, it will mean laps under 1:22 in my opinion.” [mark]. It will be 1.21.7 minutes, and that can be a good race pace for each lap.
“Today I was more like 1:22, 22.1, 22.2. That means, if I have the same race pace tomorrow, I won’t be in the top 10.”
Zarco’s poor form comes after a series of tough weekends since falling out of the battle to win on home turf at Le Mans – although he saw a slight upturn in form the last time he finished eighth at Assen.
“I don’t understand what happened,” said the Frenchman. “Maybe this is the worst of the last three weekends, it looks a bit more like the Mugello.
“I wasn’t quick at Mugello and Barcelona [it was a bit] better, and in Assen it was a different weekend, I was competitive but was just lucky enough to start in eighth place.
“Here it is another eight tenths [gap to pole] but eight tenths is like a lifetime so i don’t know what to say.
“What was better at the beginning of the season? Maybe we did well, we are still fine, but she [rivals] is it better. That’s also a way of seeing things. “