Sauber drivers Sergio Perez and Kamui Kobayashi say their car's performance is falling short of expectations at Monza after a troubled Friday practice.
After the team's stunning qualifying performance in Belgium, Sauber fell back on day one in Italy. Both cars encountered unspecified technical problems in practice, and Kobayashi said he encountered some unusual handling characteristics.
"It was a bit of a difficult day," he said. "I didn't do enough running to decide on the settings and the downforce level.
"In the morning it was business as usual and also my first run in the second session was OK. But then, after we had made some changes, the car was bouncing an awful lot. I nearly spun on the straight. However, we identified the problem but could not fix it during the session. I think we have quite a lot of work to do tomorrow."
Perez still believes another top-10 qualifying performance is possible, but agreed it had been a tough Friday.
"Overall so far I have the feeling we are a bit behind expectations here," he said. "We lose quite some time on the straights and now have to find a good aero and setup compromise. We definitely want to fight for the top 10 in qualifying tomorrow."