Banned for two years for doping, the Briton had signalled his return last season by winning the 14th stage of the Spanish
Vuelta, a 48-km time trial. But he admitted that this victory over 4.7 kms in Issy-les-Moulineaux was a real new start.
"Last year was very hard after two years without racing. It was tough mentally and physically. But this prologue was my first objective of the season. I'm very impressed with myself," said Millar, who rides for Spanish team Saunier Duval.
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In six minutes and one second, the Scot beat unheralded Czech Roman Kreuzinger by one second, Frenchman Sebastien Joly taking third place a further second adrift.
Millar, who shot to fame by winning the Tour de France prologue in 2000, said he was now hoping to keep the leader's jersey all the way down to the French Riviera and Nice, which the bunch will reach in a week.
"I'm going to defend the jersey as long as I can and hopefully take it all the way to Nice. I have a great team around me, one of the very best in the race. They might not be very famous names but they always ride in the front and will be a very valuable asset," he said.
Millar, 30, used his vast experience to master the technical course on a warm and sunny day which revealed in Kreuzinger a future tough opponent for the Briton in time trials.
At 19, the young Czech, a junior world champion in 2004, displayed impressive power and speed for his best professional finish so far.
The son of a former cyclo-cross world champion, the Liquigas rider was too fast for most of the other favourites who were rather disappointing.
American Levi Leipheimer, the recent Tour of California winner, limited the damage in 6:04 but his compatriots David Zabriskie and Bobby Julich, the prologue winner last year and the overall 2005 champion, were below par.
Most of the opposition for Millar in the next couple of stages will come from sprinters, who could take the opportunity of the flat stages ahead to challenge his lead.
In this respect, the most dangerous contender looks in-form Italian Daniele Bennati, who is only four seconds off Millar's pace.
In contrast, Belgian Tom Boonen, winner of five Paris-Nice stages in recent years, should be less of a danger, having lost 11 seconds to Millar.
Monday's 186-km first stage takes the 160 riders from Cloyes-sur-le-Loir to Buzancais.
Paris-Nice, celebrating its 65th edition, was nearly cancelled because of a row between its organisers and the International Cycling Union (UCI) over marketing rights but a last-gasp agreement was found late last week.
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