There may be a fly in the ointment if the first practice session of the new Formula One season is anything to go by.

All the talk in the pre-season build-up has centred around 'the big four' of McLaren, Ferrari, Red Bull Racing and Brackley-based Mercedes GP.

One team, though, has quietly been beavering away in the background and they came to the fore after the opening 90 minutes ahead of the curtain-raising grand prix in Bahrain this weekend.

The name of Force India's Adrian Sutil topped the timesheets for the recently-lengthened Sakhir circuit that sits in the middle of the Bahraini desert, perhaps underlining the suggestion by a few they are dark horses.

The additional eight corners has significantly increased the lap time as Sutil's best of one minute 56.583 seconds was 22 seconds slower than Jarno Trulli's fastest of a year ago, a 1:34.556.

The fact Sutil was out in front was certainly a surprise, however, this was only first practice, and like the 15 days of pre-season testing before, it was hard to judge the exact positions.

Nevertheless, the Silverstone-based team will be heartened by such a strong start, finishing 0.183secs ahead of Fernando Alonso on his Ferrari debut.

There was a further shock with the sight of the Enstone-based Renault F1 team's Robert Kubica in third, the Pole significantly overshadowing his Russian rookie team-mate Vitaly Petrov, who was down in 16th, with just under two seconds separating the duo.

Kubica headed a gaggle of drivers hovering around half a second off German Sutil, with Ferrari's Felipe Massa next up, followed by the McLaren pairing of reigning world champion Jenson Button and Lewis Hamilton.

Behind the top six, Vitantonio Liuzzi was at least in close attendance to team-mate Sutil as he finished 0.6secs down. Completing the top ten was an intriguing trio as Red Bull's Mark Webber sandwiched the Mercedes duo of Nico Rosberg and Michael Schumacher, with the former pipping the seven-times world champion.

It was 41-year-old Schumacher's first official practice session for three and a half years on his comeback outing, and he finished a full second behind Sutil, and 0.4secs adrift of Rosberg.