Jenson Button raised a few eyebrows on day one of the Bahrain Grand Prix after posting the third fastest time in evening practice.

The performance, which saw the Briton lining up behind only the pace-setting Mercedes on the timesheets, surpassed recent expectations of the McLaren-Honda package and left rivals wondering if they needed to factor a new contender into the midfield battle at round two. Button, meanwhile, remained vague on his car's true potential, but insisted that he expected to produce a similar result in the first of the day's two sessions.

"I don't really know [whether fans should get excited] yet, but FP1 was the same," he noted, "On the second run in FP1, I had higher fuel so I couldn't really get a reasonable lap time, but I think it would have been equally competitive. The car doesn't feel too bad. I came from the back-up tyre to the supersoft, which is a big leap - I think it was 3.2secs - so it's obviously going to feel good and you're probably not going to get everything out of it, but the balance is reasonable and the car is feeling nice around here.

"I gained 3.2secs and that was not fuel, that was not different modes, that was tyres and circuit improvement. It's a massive chunk and it's very difficult to do good set-up work when you're doing that sort of thing and get a positive feel.

" If you look at how far off we are off the Mercedes, that's the time you've got to gauge really. There will be cars that slip in between us tomorrow, but you've got to say that it's was a good day for us -- the best day for a couple of years. It's a good start, we didn't do anything unusual, and hopefully we can continue to improve tomorrow."

Button, running alongside rookie Stoffel Vandoorne in the absence of regular, but injured, team-mate Fernando Alonso, reported that the MP4-31 had clearly improved since round one in Australia

"It feels definitely better than Melbourne," he confirmed, "Some areas need a bit of work, especially on the harder compound, but the supersoft was reasonably good, so it's a nice place to be, a nice place to start, but there is still work to be done overnight."

Asked whether the performance could translate into improved qualifying positions on Saturday, Button remained cautiously optimistic.

"I think, when you're third in FP2, it's not because of changeable conditions or anything, so you've got to be thinking of getting into Q3 - it has to be the aim," he maintained, "We've got to do a good job as a team and make sure we don't do any mistakes, like we did in Melbourne, when other people falter. We're not competitive with the big boys, but the other teams behind them... hopefully we can fight with them."