Red Bull fastest by over 1.2 seconds, Renault its nearest challenger with Carlos Sainz Jr third, Ferrari behind, both Mercedes drivers outside the top six and slower than a Toro Rosso, 0.214s covering positions three through 10 - not to mention pacesetter Max Verstappen grinding to a halt with 10 minutes to go after dominating on pace.
Friday practice can be predictable, but it's a long time since F1 has produced an opening day of the weekend that left so many people scratching their heads and asking 'what was that all about?'.
But as mad as Mexico Friday looked, with the timesheets seemingly overturning the order established over the 18 previous weekends, there are at least partial explanations for what happened. But first, let's quantify just how mixed up things were.