Lance Stroll and Sergey Sirotkin are keeping their expectations in check at Williams following the departure of the team's chief designer Ed Wood.
The technical team changes come on the back of a mediocre start to the season for the Grove-based outfit, although Stroll succeeded in finishing eight in Baku, where the track's layout better suited the team's troubled FW41.
Williams has brought a few upgrades for the Spanish Grand prix, but both Stroll and Sirotkin are uncertain what to expect.
"We will see on Friday but for now it's too early to assess my degree of optimism," driver Stroll told Le Journal de Montreal.
"But it is time to find ways to improve. Perhaps the change in our structure will help. I don't know for now. My role is to drive," he added.
Sergey Sirotkin will be sitting out FP1 as Robert Kubica's enjoys a session in the car, a situation that doesn't delight the Russian although he hopes it will benefit the team as a whole.
"Of course it's not ideal for me, but it's an advantage for the team to have three drivers testing the car and giving feedback," said the 22-year-old.
"Every driver would prefer to do as many kilometres as possible, even on a known track. We still need to try and get the best from it. The more drivers driving the car, the wider range of the feedback you can get from it. And that is what we are going to try to do.
"It will be good to see what Robert thinks about the car compared to winter testing."
As for the car upgrades for Barcelona, Sirotkin is not sure.
"It will not happen that we will suddenly be in the middle of the grid," he said. "But we do expect to see a step forward."
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