Rossi was the first big improver; ‘The Doctor' jumping up to P2 from P9 to put himself 0.105 off leader Marquez, before it was red sectors galore on the timing screens as FP2 entered the final seven minutes.
Miller was shadowing Marquez and initially it was the Ducati man who took top spot as the pair crossed the line exchanging fastest laps.
But it wouldn't last long as Vinales took over at the top, going quicker by over a tenth.
After that benchmark was laid down, it looked like Marquez would go back to the top but a moment for the reigning champion kept him in P2.
Miller stays close
Miller (Pramac Racing) was incredibly close, however - only another 0.002 in arrears in P4. He still emerged as the top independent rider though.
Will the weather hold on Saturday and give us an almighty fight in FP3 for a place in Q2? Or have the cards been played until Q1 and qualifying?
Meanwhile, another incredible tribute to the 'Kentucky Kid' took place as the MotoGP paddock gathered on 'Hayden Hill' at Turn 18 for a historic photo opportunity.
The tribute was the perfect finale for the day on which the number 69 was retired from the premier class of Grand Prix racing.
Earlier, an emotional ceremony took place to formally retire the number, with the room packed full of Hayden's family, fiancee, friends, former rivals and teammates to celebrate the life and career of the MotoGP legend.