Djokovic, a revelation this season with five titles and a final appearance at the US Open, was a shadow of his brilliant best.
World number two Rafael Nadal, making his debut at the $2.45 million indoor event, had no such problems. The Spaniard recovered from a break down to outclass Italian Filippo Volandri 6-3, 6-1 and set up a third-round match against Swiss Stanislas Wawrinka.
Russia's Nikolay Davydenko, who won the tournament last year and is seeded fourth, overcame a sluggish start to move past Argentine qualifier Juan Martin Del Potro 7-6, 6-1.
Djokovic, who entered the Bercy hall wearing a Zorro mask which he took off when the match started, made a string of unforced errors. Santoro, double-faulted on his first match point but made amends with a backhand volley on the second to seal victory after 69 minutes. British number one Andy Murray, who had earlier stayed on course for a Masters Cup berth by beating Finn Jarkko Nieminen 7-6, 6-3. The 20-year-old Scot is one of several players fighting for the two remaining spots at the November 11-18 season-finale in Shanghai featuring the world's top eight. Murray took the first-set tiebreak 7-5 when Nieminen hit a backhand into the net.
Nieminen broke serve in the fourth game of the second set but the Briton hit back immediately before capturing the Finn's serve again in the seventh game.
Earlier, Fifth seed David Ferrer of Spain moved past American Mardy Fish 6-1, 7-6 in the second round and meets Czech Tomas Berdych, the 2005 tournament winner, who overcame Croat Mario Ancic 6-3, 6-3.
Other results (prefix denotes seeding): Second round: David Nalbandian (Arg) bt 14-Carlos Moya (Spa) 6-4, 6-4; 10-Richard Gasquet (Fra) bt Jo-Wilfried Tsonga (Fra) 7-5, 7-6(3); Marcos Baghdatis (Cypr) bt 13-Ivan Ljubicic (Cro) 6-4, 7-6(4).
Easy for Davenport
In Quebec City, American Lindsay Davenport made the most of her wild card invitation with a 6-3, 6-3 victory over seventh seed Angelique Kerber in the $175,000 WTA Bell Challenge on Tuesday, adds AFP. Facing the 19-year-old Kerber of Germany for the first time, Davenport encountered little resistance. The only other match on Tuesday to feature a seeded player was eighth-seeded Olga Poutchkova’s 6-1, 6-2 victory over Kiwi qualifier Marina Erakovic.
Other results: Second round: 5-Olga Govortsova (Bel) bt Alina Jidkova (Rus) 6-3, 5-0 (Jidkova retired). First round: Sofia Arvidsson (Swe) bt 4-Meilen Tu (US) 6-2, 6-2; Maret Ani (Estonia) bt Andreja Klepac (Slovenia) 6-2, 2-6, 6-1.
