Sergio Perez was fastest in the second practice at the Azerbaijan Grand Prix on Friday as Lewis Hamilton and Mercedes struggled on the streets of Baku.
Perez clocked 1min 42.115sec, just 0.101sec ahead of his Red Bull teammate, championship leader Max Verstappen.
"Today it was like, I finally understand how to drive this car," said the Mexican.
Ferrari's Carlos Sainz was third with teammate Charles Leclerc was fourth despite a brush with a barrier.
"It's definitely better than we expected," said Leclerc. "But it's only FP1 and FP2. The pace looks promising. Now we'll keep on working during the night and hopefully we'll be as competitive tomorrow."
Hamilton was down in 11th, more than a second slower than Verstappen.
The reigning world champion urged his team to "do whatever we need to do, I'm not going to go any faster. I don't know where all the time is."
"Honestly, I generally had a really good day; it was clean, I got all the laps that we needed, there were not really any mistakes, but just slow," said Hamilton. "There's just no more time in it. We're definitely quite a chunk down, and I think everyone will be scratching their heads and looking into the data to see how we can improve."
"The car is limited," added Hamilton. "But we'll work at it. It's not easy to be out of the top 10 when we've had pace in other places, but I don't really know why we're where we are.”
His Mercedes teammate Valtteri Bottas performed even worse, finishing 16th.
"It was very tricky for us today, clearly lacking pace," said Bottas. "It feels like it's just overall grip. The balance is not that far off."
"I think it’s going to be a long night tonight."
Azerbaijan, making its first appearance since 2019, presented drivers with a slippery and gusty circuit and Mercedes were unable to get significant results from the soft tyres.
Hamilton trails Verstappen by four points in the overall standings.
Second free practice times
1. Sergio Perez (MEX/Red Bull-Honda) 1:42.115 (22 laps), 2. Max Verstappen (NED/Red Bull-Honda) 1:42.216 (23), 3. Carlos Sainz Jr (ESP/Ferrari) 1:42.243 (24), 4. Charles Leclerc (MON/Ferrari) 1:42.436 (22), 5. Pierre Gasly (FRA/AlphaTauri-Honda) 1:42.534 (26), 6. Fernando Alonso (ESP/Alpine-Renault) 1:42.693 (24), 7. Antonio Giovinazzi (ITA/Alfa Romeo-Ferrari) 1:42.941 (25), 8. Lando Norris (GBR/McLaren-Mercedes) 1:43.018 (24), 9. Esteban Ocon (FRA/Alpine-Renault) 1:43.020 (23), 10. Yuki Tsunoda (JPN/AlphaTauri-Honda) 1:43.130 (25), 11. Lewis Hamilton (GBR/Mercedes) 1:43.156 (24), 12. Kimi Raikkonen (FIN/Alfa Romeo-Ferrari) 1:43.220 (23), 13. Daniel Ricciardo (AUS/McLaren-Mercedes) 1:43.298 (23), 14. Lance Stroll (CAN/Aston Martin-Mercedes) 1:43.812 (21), 15. Sebastian Vettel (GER/Aston Martin-Mercedes) 1:43.881 (22), 16. Valtteri Bottas (FIN/Mercedes) 1:44.184 (23), 17. George Russell (GBR/Williams-Mercedes) 1:44.557 (24), 18. Nikita Mazepin (RUS/Haas-Ferrari) 1:45.563 (23), 19. Mick Schumacher (GER/Haas-Ferrari) 1:46.095 (12), 20. Nicholas Latifi (CAN/Williams-Mercedes) 1:46.983 ( 5)