Robert Kubica put his best lap on the line as he secured top spot in final practice for the Renault F1 team, but Fernando Alonso did more than that as he piled his Ferrari into the barriers approaching Massenet and faces a race against time to be ready for Monaco GP qualifying.
Kubica defied traffic late in his flying lap to topple Red Bull's Mark Webber from the top of the timesheets, having thrown his R30 around the streets of the Principality, and survived the final few minutes of the hour-long session in which an equally-lary Felipe Massa also pipped the Australian for second spot. Kubica's time also reset the benchmark for the weekend, lowering Alonso's Thursday best by a tenth as he clocked 1min 14.806secs.
The Pole ended the morning just 0.046secs to the good, however, as Massa defied several close shaves to slot into second spot for a Ferrari team already facing one major rebuild in the two hours before qualifying. The Brazilian appeared to kiss the barriers at the Swimming Pool having already slid wide at Loews Hairpin earlier in the hour. He left the pits after having his wing 'taped up' to set his best lap.
Webber was only just over a tenth off the pace, having moved to the head of the times midway through the session, Paddock wisdom suggests that he, and Red Bull team-mate Sebastian Vettel, may have pace in reserve for qualifying but, as the traffic problems of practice showed, no-one is guaranteed a clear lap. Webber himself was forced to break hard after coming across a near-stationary Michael Schumacher at Rascasse, the German having slowed to give himself a clear run behind two cars ahead of him, while others - including Kubica and Schumacher's Mercedes team-mate Nico Rosberg - ran into notable hold-ups while trying for a time.
In the end, less than a second separated the top dozen drivers, with sevens teams included in the leading group. Lewis Hamilton, McLaren team-mate Jenson Button, Vettel, Schumacher, Rosberg, Toro Rosso's Sebastien Buemi and Jaime Alguersuari and Force India duo Adrian Sutil - who also clanged a wall - and Tonio Liuzzi all featured, with Williams' Nico Hulkenberg and Rubens Barrichello respectively 1.3 and 1.4secs adrift of the pace.
Joining the Brazilian veteran in that time bracket were Vitaly Petrov and Alonso, the Spaniard no doubt capable of more had he not destroyed the right-hand side of his F10 on the barriers climbing the hill towards Casino Square. Alonso ruefully admitted that the accident had been the result of driver error, and now faces an anxious wait to see if the car can be repaired in time for qualifying - and in a state that will allow him to escape from the opening phase of the knock-out session.
Alonso still had enough pace early in the session to see off the similarly-powered Saubers which, in turn, had a second in hand over the best of the newcomers, Lotus' Heikki Kovalainen. Virgin Racing's Timo Glock, meanwhile, brought up the rear after coasting to a halt at the harbour-front chicane after just three laps.