Romain Grosjean ended the final practice in Hungary on top after Perez's crash disrupted everyone's qualifying simulations.
With just two minutes to go in the session, Perez clipped the kerbs at turn 11, forceing him into a spin and a run into the barriers. McLaren will have a lot of work to do to get the car back for qualifying.
The crash meant that most drivers couldn't successfully complete their qualifying simulations at the end of the session, thus giving us an incomplete picture of what's going to happen in qualifying.
Fernando Alonso finished the session with the second quickest time, 1:20.898, almost two tenths off Grosjean's 1:20.730. Despite the crash, Perez was third fastest in a resurgent McLaren.
Sebastian Vettel, who topped both practice sessions on Friday was only fourth fastest today with 1:21.125. However, he looked extremely strong on long runs and completed more laps than any other drivers in the session.
Felipe Massa put the fifth fastest time in the second Ferrari, just a few thousandths of a second ahead of Lewis Hamilton in the lead Mercedes. Mercedes were in much better shape today after making some major set up changes to W04.
Mark Webber was 7th fastest ahead of Mercedes' Nico Rosberg and McLaren's Jenson Button. Adrian Sutil, who is taking part in his 100th race, completed the top 10. Force India would be looking to make into Q3 despite looking a tad slower than McLaren.
Kimi Raikkonen, who struggled throughout the session was 11th fastest. But as we said earlier, the timesheets should not be considered to predict qualifying performance after Perez crashed right at the end of the session.