Sauber are investigating the cause of Sergio Perez's qualifying accident, which put the Mexican down in 24th place on the Monaco grid.
On his first flying lap of the afternoon, Perez appeared to get it very wrong in the Swimming Pool section resulting in the Mexican driver hitting the barriers, causing damage to the left side of his Sauber.
Perez, who also lost his rear left wheel, was not able to continue and will start Sunday's 78-lap grand prix from the very back of the field.
"We are analysing what happened," Perez, who crashed heavily in last year's Monaco GP qualifying, told the BBC.
"In the Tunnel I had a lot of understeer, which doesn't normally happen.
"When I got to Turn 13 and I went into Turn 14 the car went straight.
"It's a big shame because we were so competitive. It was a big opportunity for us today."
He added: "If it's a normal race tomorrow, it will be over for us."
The team's head of track engineering Giampaolo Dall'Ara was left to lament his drivers' lack of pace as Kamui Kobayashi could only manage P12.
"The car is definitely quicker than we showed today," Dall'Ara said.
"We are very disappointed and we don't know what happened to Sergio.
"We are looking right now to see if there was a problem with the car."