SAO PAULO (Reuters) - Quadruple world champion Sebastian Vettel says Mark Webber's retirement after Sunday's season-ending Brazilian Grand Prix will be a loss for both him and Red Bull despite their frequently frosty relationship.
The 37-year-old Australian is bowing out of Formula One after 12 years and 215 races, in which he has enjoyed nine wins, to start a new career racing for Porsche in their Le Mans endurance program.
Webber, who will be replaced by 24-year-old Toro Rosso driver and compatriot Daniel Ricciardo at the champions, has been with Red Bull since 2007 and raced as Vettel's team mate since 2009.
"People tend to forget how successful we have been," Vettel, who won his fourth title in a row in India last month, told reporters at the Interlagos circuit on Thursday. "I think it has been one of the strongest pairings in Formula One.
"We didn't have the best relationship on a personal level but I think in terms of working professionally together for the team it has been very strong," added the 26-year-old German.
"Surely the fact that he will not be around next year will be a loss for the team, a loss for myself because it has always been a huge challenge. I've learned a lot from him, and I can stand up straight and say that there were many, many times and many places where I benefited from him."
In their time together, Webber and Vettel have secured four successive constructors' titles for Red Bull - making them only the third team to achieve the feat after Ferrari and McLaren - and won 46 races.
Their relations have been strained by incidents on and off the track, with the pair colliding in Turkey in 2010 when battling for the lead while in Malaysia this year Vettel ignored team orders to take the win from Webber.
Webber has also in the past accused a faction within Austrian-owned Red Bull of favoring the German, describing his own win at Silverstone in 2010 as 'not bad for a number two driver'.
Vettel has won the last eight races, a record for consecutive wins in a single season, and can equal Michael Schumacher's 2004 record with Ferrari of 13 wins in a season on Sunday.
The champion made clear there would be no special favors on either side: "I think Mark is a sportsman and he doesn't want a win to be handed over to him. I think it would be the same the other way around."
Webber told a news conference at Interlagos that he would miss some aspects of Formula One but was ready to stop.
"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. But I'm on a little bit of a slippery slope now...," he said.
"I still think I'm driving well but I don't want to be around not driving well.
"There comes a time when you've got to let go and I'll still have good adrenaline next year obviously with Porsche and that'll be a good balance."
Webber said his final race, at a track where he has twice won in the past, still felt like a normal grand prix weekend although it would undoubtedly be different on Sunday.
For all that, there were few regrets.
"I wouldn't be leaving if there wasn't things that I'm not happy to leave behind," he said.
"If there's more positives than negatives then obviously I would stay, so there's more negatives than positives... I want a fresh change, a new chapter in my life. Basically I'm ready for that, personally and professionally."
(Writing by Alan Baldwin in London, editing by Alison Wildey)