Fernando Alonso says that it is too early to say how competitive Ferrari will be in this weekend's Brazilian Grand Prix at Interlagos despite lapping just two tenths slower than Lewis Hamilton's pace-setting time in Friday's free practice sessions.
Alonso, who currently lies third in the drivers' championship 10 points behind Hamilton's McLaren team-mate Jenson Button, suffered a number of technical issues during the 180 minutes of running - including an engine failure four minutes prior to the end of FP1.
"Today was not the easiest day for us in terms of the balance of the car, in terms of issues and mechanical problems - in P1 we had an engine problem and P2 some other problems as well, sensors and things like that," said the 30-year-old Spaniard.
"It was not a smooth Friday and we need to see tomorrow in terms of how competitive we can be. I think it is difficult to know. There are things to do overnight to change the balance and to be a little more comfortable because today we struggled with the rear end of the car quite a lot."
Asked what had caused the engine failure, Alonso replied: "We are still investigating (the engine) I don't know what was the conclusion, we need to wait until it get backs to Italy and we can open it.
"Obviously it was an engine failure but we don't know exactly which part was causing the problem.
"We replaced the engine and obviously being the last race the mileage of the Friday engines are quite high - we are using very old engines for Friday - so these things can happen but we need to investigate more to see the real problem.
Alonso restated his view that his only realistic chance for victory on Sunday however would be if the predicted wet weather affected either qualifying or the race.
"I think we need to worry about what the weather is doing as well," he said. "In a dry race we are maybe not competitive enough to fight with McLaren and Red Bull. We need to be realistic.
"I understand that that has been our position over the last 10 races, to be fifth or sixth, and here it seems even more obvious. Even the Mercedes are challenging us from behind, so in a normal race it won't be easy, but P5 for qualifying and dreaming for a podium in the race.
"If it rains on Saturday or Sunday then anything can happen and it is much more open."