March 25 (Reuters) - Red Bull are beginning to sound more like the teams who were chasing them last year after both cars failed to finish on the podium in the Malaysian Grand Prix on Sunday.
World champion Sebastian Vettel started fifth on the grid and limped home 11th after contact with the HRT of Narain Karthikeyan punctured his left rear wheel and damaged the brake duct.
"He came up to Karthikeyan who seemed to have brain fade ...," Vettel's Red Bull team boss Christian Horner told reporters.
"That was frustrating for Sebastian because for sure at least a fourth place finish was on for him today," Horner said.
Horner said the damaged brake duct, which feeds air to the brakes to cool them down, meant Vettel's brake temperatures rocketed, prompting the team to ask him to retire the car.
But a malfunctioning radio meant Vettel did not hear the call.
"We could see the left rear brake going into a thermal runaway and out of control and that's why we wanted to try and stop the car from a safety point of view," Horner said.
Vettel's team mate, Mark Webber finished fourth despite not being entirely comfortable on the intermediate tyres he put on after the rain interrupted race had been re-started.
"That was a very, very, very long stint. Not very Formula One to be driving around with that little grip," Webber said.
"And then when the track started to go dry I felt much happier obviously and we were going a lot more right," said the Australian who was catching third-placed driver Lewis Hamilton towards the end of the race.
Red Bull have struggled this season with McLaren dominating the first two qualifying sessions.
The Adrian Newey-designed cars did show far more promising race pace in last week's season opener but did not quite have the speed to challenge Jenson Button's winning McLaren.
The Milton Keynes-based team comes away from the opening two races with 42 points compared with the 72 they had at this stage last year.
"We know we've got things that we can improve on and that's what we'll be focused on for China," Horner said. "But it's fairly unpredictable for the moment.
"Consistency will be important all the way through." (Editing by Ed Osmond)
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