Mark Webber said he feels Red Bull made a mistake in switching him to a three-stop strategy in the Japanese GP.
Webber was second behind Lotus's Romain Grosjean with team-mate Sebastian Vettel in third when the decision was made but Vettel ended up winning from the Frenchman.
Webber said: "We probably left a bit out there and you can't do that. Seb is going to capitalise.
He said he was "kicking himself" and had questioned it during the race.
Webber started on pole ahead of Vettel and Grosjean, who made the best start to lead the two Red Bulls in the first part of the race.
The three circulated together until mid-way through the race while Red Bull were trying to come up with a way to get both cars ahead of the Lotus.
They switched Webber to a three-stop strategy with the aim of giving him fresher tyres and forcing Lotus to respond with Grosjean, which they did.
Vettel did a long second stint and came out of his second stop ahead of Webber and just behind Grosjean, who he quickly passed. Webber also rejoined behind Grosjean after his final stop but was unable to pass the Frenchman in time to attack Vettel.
Webber said: "We can't pass him on track. It was on my mind to undercut him [by stopping earlier] in a straight two-stop so when we had to squeeze up on the back of him in a half two-and-half-stop strategy… That's what the team decided to do and I have to go with it and do my best.
"I think we were trying to beat both people. It wasn't easy to cover both, we were trying to put pressure on Romain for the win.
"We were still sticking to our two-stop after the first round of stops, so I thought: 'OK the gaps are under control.'
"Seb went a bit longer on the first stop. He was going to be maybe a handful on two-stop towards the end of the race and then they rang up and said OK we're going to go for a three.
"I thought 'OK that's a bit different but let's try and make it work.'
"Look, we tried to win the race against Romain but obviously Seb can do a different strategy because I was trying to beat Romain on a different strategy.
"It's very hard to say in the end what was the right strategy, I asked the team was it the right strategy, even in the race. I was not 100% sure, but once you've committed you have to go for it."
Red Bull team boss Christian Horner said: "The first stint dictated that for us.
"Mark put Grosjean under quite a lot of pressure and went through the tyre phases very, very quickly. To the point he had run out of tyres by the time he pitted, which was too short for us in our own minds to make a two-stop really work because he'd effectively run out of tyres in that last stint.
"Sebastian went about five laps longer than we expected him to [in his second stint] and when he pitted he used those tyres incredibly well to close and pass. He then knew he was effectively racing Mark.
"Mark closed in on Grosjean pretty quickly but unfortunately he didn't go past Grosjean very quickly which killed off any chance he had to catch Vettel."
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