Valtteri Bottas believes Mercedes have some work to do ahead of qualifying despite finishing second and third behind Red Bull's Max Verstappen in the second practice session for the Mexico City Grand Prix.
The Finn started the day strongly by posting the fastest time during FP1, with teammate Lewis Hamilton finishing just behind him in second.
However, Max Verstappen responded with the quickest time later in the day, a full 0.424s faster than Bottas, who admits Mercedes have some work to close the gap to Red Bull.
"The start of the day was quite tricky with low grip," Bottas said after Friday practice. "It was really dusty [on] track, and that's why it was quite difficult to get a proper read on how the car actually is, but I thought it wasn't far off how it should be.
"We could really fine-tune for the second practice, and it didn't feel too bad, but there's still definitely time we need to find, because Red Bull seem a bit quick.
"They definitely seem quicker today, at least on the single lap. They have really strong pace on the Soft tyre. We need to find a bit of time if we want to want to fight for the pole."
Lewis Hamilton blamed a lack of downforce for his gap to Verstappen, with the Briton finishing half a second slower than his World Championship rival in FP2.