Nick Heidfeld did just enough to prevent Lewis Hamilton from heading into qualifying for the Chinese Grand Prix with a hat-trick of free practice successes under his belt.

The BMW Sauber driver capped a solid session for the Hinwil/Munich team by posting a lap of 1min 36.061secs to keep Hamilton out of top spot by 0.074secs, as team-mate Robert Kubica sandwiched the McLaren man in second place.

Hamilton had appeared set to reprise his Friday form after heading the pack for much of the hour, especially while everyone was lapping on the harder of Bridgestone's two tyre options, but Heidfeld managed to find just enough after switching to the softer rubber in the final minutes. Only Sebastien Bourdais and McLaren team-mate Heikki Kovalainen had the temerity to unseat Hamilton before Heidfeld's last ditch assault but, on both occasions, the Briton hit back almost immediately.

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Kovalainen eventually ended up fourth fastest after being pipped by Kubica, who underlined that he remains a credible threat to the Hamilton-Felipe Massa title battle despite needing a hatful of points this weekend. The Pole was only 0.089secs slower than team-mate Heidfeld.

Behind Kovalainen, Jarno Trulli confirmed the upturn in form he and Toyota showed in Friday's second session, while both Nico Rosberg and Bourdais remained fixtures in the top ten. David Coulthard, Kazuki Nakajima and Nelson Piquet Jr rounded out the first half of the timesheets.

Conspicuous by their absence from the leading group were the two Ferraris and the second Renault of Fernando Alonso. The Spaniard spent a deal of time in his pit garage and only posted the 16th best time of the session, despite still managing to cover as many laps as his rivals, while Massa and Kimi Raikkonen were little better of in twelfth and 13th respectively. Ferrari, however, often goes its own way on Saturday morning and both are expected to be factors in qualifying.

Surprise of the session was Rubens Barrichello, the under-pressure Brazilian taking his Honda to eleventh spot while team-mate Jenson Button sat 15th, and Sebastian Vettel, who again could not match team-mate Bourdais' pace in the second of the Toro Rossos.

A Hamilton trip down the pit-lane escape road aside, the only major incident of the hour again seemed to target Mark Webber, whose Red Bull began emitting smoke and flames midway through and looks likely to condemn the Australian to a ten-place grid penalty should his engine need to be changed.