Sauber's head of track engineering Giampaolo Dall'Ara said the team faces a long night working out why it was so far off the pace in Friday practice in Singapore.
Sergio Perez, fresh from his third podium finish of the year at Monza, was only 15th fastest with team-mate Kamui Kobayashi one place further back as the pair struggled with the balance of their respective cars.
With Perez claiming that his car felt 'inconsistent and unpredictable' and Kobayashi stating that the performance of the team was 'rather weak', the team was left scratching its head as to what had gone wrong, with Dall'Ara insisting that the team would work hard to get to the bottom of the problem.
“Despite the rain affecting the first session and the red flag affecting the second session massively, we were able to complete our programme,” he said after the team managed to try out a series of new components on the C31 in the opening session. “However, the problem is that we are significantly too slow. There seems to be a major problem, but we don't quite understand what it is.
“We will certainly have a long night analysing all the data. First we have to understand what's wrong, and then we will have to find the right measures to cure it.”