Mercedes' hopes of annexing the front row of the grid for a second straight F1 weekend were ended in the opening phase of qualifying for the Bahrain Grand Prix after a late improvement from, of all things, a Caterham dumped Michael Schumacher out of the session.

The seven-time world champion was among a cluster of leading names who all believed that they would be safe with the times they posted earlier in the 20-minute session, only to find themselves sinking down the order as the track continued to evolve. At one point, it appeared that Jean-Eric Vergne and Bruno Senna would be those ignominiously highlighted in the Q1 headlines, but Schumacher found himself on the cusp of the drop zone as Heikki Kovalainen completed his final qualifying effort.

The Finn improved by around two seconds and it was enough to dump the grid's most experienced driver, who posted a scruffy lap, out at the first time of asking. Had any more drivers been on track, then the likes of Jenson Button, Lewis Hamilton and Fernando Alonso could also have been in trouble but all three escaped, no doubt wiser to the dangers that could lurk in the remainder of the session.

Schumacher, who claimed a defective DRS component, and Vergne - for the third time in as many races - will be joined on the outside looking in by the usual suspects for the remainder of the session. While the Frenchman also compounded his session by missing the stewards' signal to report for a weight check, he currently lines up ahead of Vitaly Petrov, Charles Pic, Pedro de la Rosa, Timo Glock - who left it late to evade the 107 per cent mark - and Narain Karthikeyan.

To emphasise how much the evolution affected the order, the top ten at the chequered flag read Sergio Perez, Daniel Ricciardo, Mark Webber, Romain Grosjean, Kamui Kobayashi, Sebastian Vettel, Felipe Massa, Bruno Senna, Kimi Raikkonen and Nico Rosberg.