"It's pretty close," said Vettel.
"If you look at the opposition then Ferrari and Lotus were strong today and I think it will be close in qualifying.
"It's important to work with the tires around the track. I wasn't so happy with my short runs today - but that's why we have the Friday practice sessions I guess; I was happier with the longer runs.
"The tires still seem to be the dominating factor. The car seems quick, so we have to make sure we use that and then we should be on the right page."
Lewis Hamilton, who has recorded two podium finishes so far this season, found life more difficult after finishing the day 10th fastest.
"We're working as hard as we can and we just need to find some more time from somewhere," he told reporters.
"I don't really know where we are losing it. They have changed the car this weekend, changed the settings for what they think the track needs but I'm not convinced it is the right way to go.
"I don't know if they are right or wrong but we were struggling for pace today... But I am sure we will find it."