Alonso confessed that he is lacking confidence in the AMR23 after uncharacteristically suffering big spins at the high-speed track on both Friday and Saturday.
Ultimately, he couldn’t better 13th in qualifying, while his team-mate Lance Stroll was only 18th.
“Very tricky,” said the Spaniard when asked by Autosport about what the incidents said about the car. “Yesterday [Friday] at the high-speed corners, I lost the car, today on the kerbs, I lost the car.
“It seems that we are on the edge always on the grip. And we've been slow in every session. So it's not a bad qualifying, or anything like that.
“We have been struggling the whole weekend. So yeah, tricky. We need to work all together to get back to our best level, which is obviously not the one we are showing."
However, Alonso stressed that the disappointing performance in Mexico wasn’t just about the car.
"This weekend has been particularly difficult for me,” he said. “I don't know, maybe Lance was a little bit more confident this weekend, but I was not.
“I was not doing a good job, this weekend, I felt always on the backfoot, and I was always not trusting the car.
“And as I said, a big spin yesterday at high speed could have been into the wall or anything like that. So I was not at my best either. So we need all to improve."
Aston is focussing on its new package in Mexico after splitting the cars in the US GP, and Alonso believes that it’s the right decision.
"Obviously, we had the Austin race also, which we used as a compare between the two packages,” he said. “And the results were clear in favour of the new package.
“So we don't have any concerns about that. But it seems that we are not very confident now on the car. Driving, we cannot extract the maximum. And this is penalising a lot."
He added: “Also in this track, we were losing like one or two tenths per corner. It's not just one sector that we are just missing. Now the lap time is just gradually slow.
“So we need to find more performance. As I said, everyone is trying to do their best. So I still feel confident that we will show better from now until Abu Dhabi.”
Alonso suggested that the current problems with the car go beyond specific set-up issues.
"I don't think it's the set-up,” he said. “We've been trying different set-ups a lot lately. Since Singapore, I think we've been experimenting a little bit more with the car.
“Also in Austin, we had the perfect opportunity, starting on the pitlane, to really experiment even further.
“We had the three sessions here. So I don't think is just the set-up. So it's more up to the package and us drivers to feel a little bit more confident."
Alonso still believes that he can have a strong race on Sunday: “We scored points in Austin starting from the pit lane. So tomorrow, hopefully we can still score points starting on the grid.
"I think the temperatures and running behind cars is always a big penalty here in Mexico, because of the temperatures and things like that.
“So it's going to be tough for everyone. It's a race to see the chequered flag, and we’ll see what happens in the front as well."
