Jenson Button thinks McLaren will have to look to him to win next year’s world championship.
With Lewis Hamilton leaving for Mercedes, Button - to contest his fourth season at McLaren next year - will be paired with the young Mexican Sergio Perez.
Before Hamilton decided to leave McLaren, Button said he hoped the 2008 world champion stays in 2013.
Now facing the prospect of sharing a garage with 22-year-old current Sauber driver Perez, he said at Suzuka: "Having just one experienced person in the team does change things but (that’s) is something I love.
"I’m not underestimating him (Perez)," Button insisted. "He is inexperienced compared with Lewis and it will be his first year, but he will still be quick.
"There should be more consistency in his speed the following year but I will definitely be the person McLaren turn to if they want a world champion next year."
Button admits he is "very surprised" Hamilton chose Mercedes over McLaren for his future.
"Because every season you race for this team you win grands prix," he explained.
"We all have different challenges and things we want to achieve. He wants to try something new."
F1 chief executive Bernie Ecclestone told the Express newspaper: "Lewis wanted out of McLaren because he felt unhappy there.
"He spoke to me and I told him he should go where he felt he would feel good if he could make a deal that suited him."