Sebastian Vettel was left frustrated after colliding with the HRT of Karthikeyan in the Malaysian GP, forcing the German double world champion to pit for a new wing, resulting in an eleventh place finish.
Having started in fifth, Malaysia was a poor weekend for Vettel, who isn't enjoying anywhere near the same level of dominance he had become used to over the past two seasons.
"Most crucially we lost radio communication and that makes it very difficult in these conditions to know what's going on," Vettel said. "Nonetheless we did our maximum today and got up to fourth. To then lose the race how I did is very frustrating.
"Some people need to look more where they are going. Today it was crucial to come in at the right time. Having no radio meant we were delayed getting the messages and I didn't hear anything from the team at the end.
"There were problems with the car after the incident, but I wanted to see the chequered flag. There were no points for me today. Before the incident with HRT the way the race had unfolded was good for us I think, so it's frustrating to lose the race like that."
The Malaysian GP was stopped after just nine laps due to heavy rainfall making track conditions too dangerous to race on, forcing the teams to park on the grid for an hour until the weather improved.
The race was restarted behind the safety car, which soon pitted to allow the race to continue as normal. As the track dried out drivers piled into the pits for intermediate and then dry tyres in a race that was all about staying out of trouble and changing tyres at exactly the right time.
Team principal Christian Horner said: "We had lost all radio contact with Sebastian, which meant we could only speak with him via the pit board. After his stop he came up to the HRT who hit him and caused a puncture. The incident caused damage to the rear brake duct, which went into thermal runaway, so we wanted to stop the car before the end from a safety point of view."
Vettel's Red Bull Racing team-mate Mark Webber finished fourth - the same position he had qualified in.
Webber said: "It was busy with a lot of calls going on at the re-start and with the tyres. My stint on the intermediates after the red flag was tricky and I didn't have much confidence. When I went onto the dry tyres, I felt much more confident, but it was a little bit too late then.
"You've got to take your hat off to Fernando and Perez today, there were some good calls made at the front. It was a mixed-up race and it was good to get some points. There were some great strengths to take from this weekend.
"The team has been working really hard, so thanks to them. We know there will be more opportunities in the future."
Cyril Dumont of Red Bull's engine supplier Renault said on Sunday: "Unfortunately for us, today is a race to forget. There is already a lot of gambling when you have these conditions and if you add the issues we had - which was no radio communication with Seb for most of the race and with Mark for parts of it - then it made it even more difficult."
Red Bull Racing will be looking to improve dramatically to close the gap between themselves and McLaren before the next race in China on 15 April.