CALAMA, Chile - Former Dakar rally champion Carlos Sainz' 2013 title bid ground to a halt in the sands of Chile. The 2010 champion admits he may never return to take on the gruelling event.Sainz was forced to retire when the engine on his Buggy failed at the 172km mark of the 438km sixth stage, bringing an end to his roller-coaster Dakar chase.After winning the first two stages he fell way out of contention.'I'M NOT SURE I'LL COME BACK'Sainz said: "I'm not sure whether I'll come back. I've had a lot of problems since the start and today just took the biscuit. Something must have broken in the engine, but I don't know exactly what. It just happened all of a sudden."There wasn't any temperature warning or anything. It's a new vehicle which hasn't been driven that much. It all happened very quickly," he said.Sainz's team mate Nasser al-Attiyah had a much more successful Stage 6. He slashed 10-time champion Stephane Peterhansel's lead by more than eight minutes as the 2011 winner stormed to victory on the stage.Al-Attiyah started the day at 9min54 behind defending champion Peterhansel, but finished just 1min18 off the overall lead, winning his third stage of the Dakar 2013.Wheels24 will be following the 'Dakar' rally throughout the race. Keep up with things on our Dakar Rally section.