George Russell can use his Mercedes test in Bahrain to help Williams identify their main weaknesses.
As a junior driver at the German manufacturer, the Briton was drafted in to drive the W10 on the second day of running in the desert and would top the timesheet as a result.
"It was an incredible experience and an experience not many drivers get to try," Russell commented in Shanghai on Thursday.
"They are currently leading the world championship, are a world championship-winning team and arguably the fastest car on the grid at the moment.
"So, for me, for us in our current situation where we are at the back, it was a great opportunity to know what we should be aiming for."
Russell's best time that day was 2.7s faster than he achieved in qualifying in the Williams, and he was asked if the difference between the two cars could be felt "in every corner".
"I'd say the difference is as expected," he replied. "You look where Mercedes is, you look where Williams are, the difference was absolutely as you'd imagine."
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With the knowledge he gathered in the W10 though, Russell said he at least now knew the target that Williams should be aiming for.
"Obviously we did agree that I'm not going to come back and share confidential bits," he explained.
"But I'm more than capable of coming back and saying, 'Their car is doing X in these corners and our car isn't and this is what we need to be working towards'.
"It was a very good test. We know they have more downforce than us but it's more to it than just having more downforce."
