George Russell topped Friday practice for Mercedes at the Miami Grand Prix but has warned that the session "means nothing".
Mercedes has struggled for pace this year with the team suffering from porpoising more than many of its rivals.
In a bid to unlock pace from the W13, Mercedes arrived in Miami with a number of upgrades to confirm its development direction.
The immediate results appear to be promising with Russell fastest on Friday and Hamilton just 0.241secs behind in fourth - the pair separated by Charles Leclerc and Sergio Perez.
Asked to give a message to the Mercedes fans after topping the Friday session, Russell replied: "What I'd say is that practice means nothing and we go again."
Mercedes porpoising "will always be there"
Porpoising is something F1 teams have quickly had to adapt to and the phenomenon was again a visible issue down the long back straight in Miami.
"I think we know that it will always be there but maybe it is working at a lower range compared to where we were previously," explained Russell.
"But, for sure, on that high-fuel run I was feeling it and it didn't seem to be any better. But if we can manage to do that with the car lower to the ground then we see the rewards.
"But you generally have some races that go in your favour, some that go against you.
"I think Imola obviously wasn't a strong circuit for us but so far from what we see, the car is working well around Miami."
Asked for his thoughts on the Miami International Autodrome, the Mercedes driver added: "It's unique.
"I was a bit unsure how I was going to take to the very slow-speed, tight section underneath the bridge and it's still a bit of a headbanger through there.
"That's the only thing that is a little bit tricky but for the rest, they've done an amazing job."
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