Ross Brawn says Mercedes isn't confident that it has sorted its tire woes from the Bahrain Grand Prix.
Although the team believes that it has made progress with its degradation issues, Brawn says that it is still unsure about its chances of keeping Nico Rosberg and Lewis Hamilton at the head of the field.
"The race is the key part and that is what ultimately counts," said Brawn, when asked if the team was more confident about its prospects than it was in Bahrain. "It is better if you start at the front, as we are, but having a good set-up and good usage of the tires is absolutely critical.
"We have spent a lot of time this weekend devoted to it, so I don't think we could have done any more work. But quite frankly we won't know until tomorrow, because you don't know what shape the others are in. We were better today on our race sim than we were yesterday, which is good, but whether it is enough, we don't know.
"The key thing for us is to run our own race and not try and outrace other people who are better with their tires, because when you do that you do twice as much damage. So we will run our own race and see where that puts us."
RACE DAY PLUNGE POSSIBLE
When asked if there was a chance Rosberg could drop from pole to ninth like he did in Bahrain, Brawn said: "I think he could do. The thing with the tires we have at the moment is that everyone out there on track is trying to drive to the limit of them.
"Once you exceed the limit the tire is gone. It is not a tire that you can take over the limit, cool it down and then come back again. Everybody out there is having to manage the tires in the best way they can. I think almost any track you go to you can damage tires and spoil your race - be it Bahrain, here, Monaco, Montreal.
"It is up to the drivers and team to deal with that in the best way, and the smartest ones will succeed."
Rosberg reiterated that careful approach, saying Mercedes should not expect a dramatically different experience from what happened in Bahrain.
"I am very cautious because Bahrain was very exciting on Saturday and not a nice experience on Sunday - not enjoyable. So I have a bit more caution today, but I am still very happy with pole. It is a great feeling.
"I am sure we have done improvements for the race but the target is to be better than last time. We should not expect massive steps. We want to be a bit better than last time. Lewis finished fifth in Bahrain so that should be the realistic target."