Felipe Massa has warned championship leader Jenson Button that he has to learn to deal with the pressure of battling for the F1 drivers' title, otherwise he could end up throwing it all away.

Button had a fantastic start to the season and won six of the first seven races. However since the British Grand Prix back in June, the Englishman has struggled and he now lies just 16 points up on his Brawn GP team-mate, Rubens Barrichello, with five races left and a possible 50 points up for grabs.

Speaking to British broadsheet newspaper, The Guardian, Massa added that his compatriot is a big threat.

"At the start of the season everything was nice, everything was easy for Jenson. He was in a new team winning six out of the first seven races. But now we have races where things are more complicated," Massa stated on the eve of this weekend's Italian Grand Prix at Monza, round thirteen in the 2009 FIA F1 World Championship.

"So for me the pressure has had a big impact on his mind, and he needs to deal with it better. If he does not cope with the pressure he will not win the championship.

"Look at me, last year I came to Brazil six points behind Lewis Hamilton and I almost won the championship. Rubens Barrichello has five races to close 16 points. It's a big possibility. But it depends on Jenson.

"If Jenson carries on in this bad way it will help Rubens a lot. In my opinion, Jenson has gone down because of the pressure. It's the only reason.

"In the earlier races he was almost half a second quicker than any of his rivals. You win the race easy and there is not so much pressure.

"That's different to fighting hard for the championship. Now he has a different kind of pressure."