The Spaniard teamed up with Lucas Cruz in January 2010 to edge out Volkswagen team-mate Nasser Al-Attiyah and atone for his experience in 2009 when he was leading until crashing out on the 12th stage.
Sainz, 48, also won the Silk Way Rally for the second time in September and, given such winning form, is confident he can retain his Dakar title.
He said: "With Lucas Cruz we make up a good team. We have won all the races in which we have entered. I can't wait to start the race. I want to hold on to my title.
"I know that the competition will be fierce, but that's entirely normal and is to be expected.
"As for me, as always, I'll only be thinking about how I'm going to race and to do my job well.
"As usual, I'll be racing at my pace and in my own special way."
Giniel de Villiers, winner in 2009 and placed seventh in 2010, admits he has not had the best of preparations, having not been competitive since the Silk Way Rally in Russia in September.
He said: "We haven't really been able to drive in race conditions since the Silk Way Rally, which isn't the best situation.
"Mind you, the car is working well. On the Silk Way Rally, I was still driving the old model.
"Even in just the tests in Morocco, we could feel the improvements in the cooling system and engine power.
"Of course, the aim is to do as well as in 2009. Last year, we suffered a lot, but that's in the past.
"During the Silk Way Rally, we showed that we were quick again. There is a good atmosphere in the team. We're expecting a tough struggle between us, but that's a good thing, it's healthy for the team."
Today's start sees the drivers leave the Argentinian capital and drive 370 kilometres north-west to Victoria in readiness for tomorrow's first full race day.
The route takes the competitors across Argentina and into Chile and is the third consecutive year the race has been held in those two countries.