Mark Webber grabbed the fastest time in a crazy final Montreal Formula 1 practice, as barrier damage halved the session and the track dried with moments remaining.
Half the session was lost to barrier repairs, required following a heavy crash at Turn 11 in a Ferrari support race. With Formula 1 regulations stipulating a minimum two-hour gap between practice and qualifying, and television schedules precluding a delayed start to qualifying, the morning session had to be truncated.
Adding to that frustration were the fluctuating track conditions. Although the wait meant some of the moisture from earlier rain had gone, the circuit was still too treacherous for slicks when practice finally got underway.
Sauber's Esteban Gutierrez emerged quickest of the 14 drivers who went out on wet or intermediate rubber, but many preferred to sit it out until there was a dry line. That was not the case until the closing moments, which effectively turned the session into a single-lap shootout with all 22 drivers out at once dodging through traffic on slicks.
The top spot changed hands a head-spinning 11 times in three minutes, as quicker times were set with every moment on the ever-improving track. It was Webber who finally emerged on top for Red Bull, 0.353 second faster than Adrian Sutil's Force India.
Friday pacesetter Fernando Alonso was back in fourth in the top Ferrari, between Lewis Hamilton's Mercedes and Sebastian Vettel's Red Bull.
Inevitably the chaos offered an opportunity for an underdog surprise, and Max Chilton provided one as he put his Marussia 14th.
Despite the congestion on the circuit and the slippery surface, the only minor incidents were spins for Pastor Maldonado and Daniel Ricciardo.
Pos Driver Team Time Gap Laps
1. Mark Webber Red Bull-Renault 1m17.895s 7
2. Adrian Sutil Force India-Mercedes 1m18.248s + 0.353s 8
3. Lewis Hamilton Mercedes 1m18.732s + 0.837s 7
4. Fernando Alonso Ferrari 1m18.977s + 1.082s 10
5. Sebastian Vettel Red Bull-Renault 1m19.131s + 1.236s 6
6. Nico Rosberg Mercedes 1m19.457s + 1.562s 7
7. Paul di Resta Force India-Mercedes 1m19.496s + 1.601s 6
8. Felipe Massa Ferrari 1m19.750s + 1.855s 9
9. Jenson Button McLaren-Mercedes 1m19.790s + 1.895s 9
10. Kimi Raikkonen Lotus-Renault 1m20.316s + 2.421s 8
11. Romain Grosjean Lotus-Renault 1m20.596s + 2.701s 9
12. Pastor Maldonado Williams-Renault 1m21.035s + 3.140s 12
13. Daniel Ricciardo Toro Rosso-Ferrari 1m21.364s + 3.469s 7
14. Max Chilton Marussia-Cosworth 1m21.652s + 3.757s 9
15. Nico Hulkenberg Sauber-Ferrari 1m22.021s + 4.126s 14
16. Esteban Gutierrez Sauber-Ferrari 1m22.720s + 4.825s 15
17. Jean-Eric Vergne Toro Rosso-Ferrari 1m23.058s + 5.163s 7
18. Giedo van der Garde Caterham-Renault 1m23.132s + 5.237s 14
19. Sergio Perez McLaren-Mercedes 1m23.309s + 5.414s 8
20. Charles Pic Caterham-Renault 1m23.620s + 5.725s 12
21. Valtteri Bottas Williams-Renault 1m24.317s + 6.422s 12
22. Jules Bianchi Marussia-Cosworth 1m26.195s + 8.300s 9