AP Sports Writer
SAO PAULO (AP) -- Mark Webber is at the season-ending Brazilian Grand Prix already looking forward to new challenges after Formula One.
Webber said on Thursday he's "relaxed" heading into Sunday's race at Interlagos, and was not having second thoughts about his decision to drive away from racing's top series.
The Australian admitted he will miss some aspects of F1, but was ready "personally and professionally" to end 12 seasons in F1.
There were more "negatives than positives" for him at F1, he said, so he was looking forward to a "fresh change" and a "new chapter" in his life driving for Porsche's endurance program next year.
"I think on Sunday it will be a little bit different, but it still feels like a normal race at the moment," he said. "So looking forward to Sunday in many ways, in terms of obviously pushing for a good result, but also I'm ready to stop and looking forward to the extended winter that I'll have and the new challenges around the corner."
Webber said "the fire was not quite" there anymore for him in F1, and having a difficult relationship with Red Bull teammate and four-time world champion Sebastian Vettel also didn't help.
"I wouldn't be leaving if there weren't things that I'm happy to leave behind," Webber said. "If there's more positives than negatives, then obviously I would stay. There's more negatives than positives."
Vettel said people don't have an accurate impression of his relationship with Webber and tend to forget how successful they were together.
"It has been one of the strongest pairings in Formula One," Vettel said. "Obviously we didn't have the best relationship on a personal level but I think that in terms of working professionally together both of us have tried very hard to improve the car and surely the fact that he will not be around next year will be a loss for the team, a loss for myself."
The 37-year-old Webber said he was in a "slippery slope" in terms of his driving ability.
"You've got to be careful not to test it too much in terms of performance and what you used to be able to do," he said. "I still think I'm driving well but I don't want to be around not driving well."
Webber will be replaced by countryman Daniel Ricciardo, a 24-year-old who raced for Red Bull's sister team, Toro Rosso, this year.
Webber has had nine wins and 32 podium finishes in 216 race starts. He started from the pole position 13 times and had 18 fastest laps. He twice finished third in the drivers' championship, in 2010 and 2011.
"Getting out of the car Sunday there will be a few things that will be for the last obviously in terms of Formula One, but I'm pretty relaxed at the moment and looking forward to the race," said Webber, who won in Brazil in 2009 and 2012.
Webber said he will miss certain "rewarding" situations in F1.
"Obviously, driving the car on the limit at certain venues is still very satisfying, no question about it. You've got Suzuka, Spa, Monte Carlo ... so I'll miss some of that.
"It's inevitable that you are going to miss certain parts. But there comes a time when you've got to let go and I'll still have good adrenaline next year obviously with Porsche and there will be a good balance."
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