SOCHI, Russia, April 30 (Reuters) - Lewis Hamilton was left puzzling a 'very odd weekend' after struggling to fourth place in Sunday's Russian Grand Prix while Mercedes team mate Valtteri Bottas celebrated his first Formula One victory.
"I can't explain it right now," the Briton, still second in the world championship but now 13 points behind Ferrari's Sebastian Vettel, told reporters.
"We'll do some work over this week to fully understand it. I have some feelings about how it (the car) felt in the race and qualifying, I have some ideas. Lots of work will be done to figure it out."
Hamilton arrived in Sochi as a two-times winner at the Olympic Park street circuit, a track where only his Mercedes team had won since the first race there in 2014, but he struggled to find his rhythm.
Bottas, who had largely the same set-up, was consistently quicker and out-qualified him for third place on the starting grid behind the two Ferraris.
While Bottas made a scorching start to seize the lead into the first corner, the triple world champion was feeling the heat.
"Why is my car overheating?" he asked at one point. "I'm out of the race (to win) now," he added, with about two-thirds of the distance remaining.
Hamilton, whose bid for a fourth title last season was wrecked by reliability issues, finished 36 seconds behind the winner.
It was the first time that he had finished off the podium since Malaysia in October 2016, when his engine expired while he was leading the race in what was ultimately a championship-deciding blow.
"In the race I had overheating but I think I could have kept up with the guys ahead but I should have been further up with better pace in general," he said. "And that was lacking from Saturday onwards.
"From probably lap five onwards I had to just slow down and stay in fourth (place). A lot of turning down of the settings and (power) unit and then one of the cylinders was cutting because of the temperature issue.
"So I was going to be fourth from very early on."
Team boss Toto Wolff said Mercedes had not been able to give Hamilton the car he needed. (Editing by Clare Fallon)