More bad weather on Friday during the second day of the final round of pre-season testing hampered all the teams in their preparations and Button said after his run: "I need another day in the car, really. I'm happy with the progress we made today, but I still feel there is so much more we need to do before the first race.
"Making setup changes does take a bit of time. We do need to make improvements over the next couple of days. It will be nice to race in slightly warmer conditions so it's comparable to what we'll find in Melbourne."
Asked whether he was alarmed, Button added: "That's not a word I would use. I'm not worried, not alarmed. I'm looking forward to doing another day's testing, it's very much needed."
Button picked out Mercedes as the most impressive team here – the marque that now employ his former team-mate Lewis Hamilton and will soon welcome McLaren's technical director, Paddy Lowe.
Button said: "I think we all hope we're going to turn up at the first race and be competitive. I'd say that one team that has been consistently quick on their runs is the Mercedes, more than anyone else."
McLaren, though, are not the only team to have been frustrated by the rain and low temperatures in Barcelona this week. Sebastian Vettel was in the same slow boat. Red Bull's world champion said: "I did not do too many laps. It was too cold and difficult to make the tyres work properly. It is difficult to compare things that you are testing.
"It is very difficult to know where we are in terms of pace. We have a rough idea and it is fine. We are happy with the balance and the way the car behaves but we will not know if that is enough.
"There is still lot more to do and these conditions are very different to what they will be like in Melbourne. We have learned a little bit but hopefully we will learn some more on Sunday."
Meanwhile Jules Bianchi's disappointment at missing out on a Formula One drive with Force India has quickly been forgotten after the Frenchman was awarded the second seat at Marussia.
Luiz Razia, the Brazilian who was initially confirmed as the replacement for Timo Glock last month, has had his contract terminated by the Banbury-based team with immediate effect.
The team principal, John Booth, said: "Having made clear the basis on which we must operate in 2013, and given the steps we had taken to put that new structure in place, we had no alternative but to remain true to the principles which we had identified as being key to securing our long-term future."
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