But David Ferrer is just behind Simon, with James Blake, Stanislas Wawrinka and Australian Open finalist Jo-Wilfried Tsonga all hoping a good showing at the Bercy indoor arena will help them qualify for the prestigious year-end championship.
In Sunday's first round action, Tommy Robredo of Spain and Dmitry Tursunov of Russia advanced to the second round in straight sets over their French opponents.
Robredo beat Jeremy Chardy 7-6 (4), 7-6 (5), and Tursunov defeated Adrian Mannarino 6-3, 6-2.
Robredo saved the only break point he faced in the first set, while Tursunov broke Mannarino's serve five times in a comfortable win.
Tursunov next plays third-seeded Novak Djokovic in the second round, while Robredo faces No. 15 Fernando Verdasco.
Last year, Frenchman Richard Gasquet jumped from 13th to eighth and took the final spot for the Masters Cup by reaching the semifinals in Paris.
Gasquet pulled out on Sunday because of an injury to his right elbow.
"I felt the injury during the Madrid (Masters) tournament,'' Gasquet said. "Of course I am very disappointed.''
The 14th-seeded Gasquet, who may need an operation on the elbow, will be replaced by a lucky loser from qualifying.
Roddick dented his chances after losing to Robin Soderling in the quarterfinals of the Lyon Grand Prix on Friday. Simon picked up points there by reaching the semis, and Roddick could play Simon in the third round in Paris.
Top-ranked Rafael Nadal, 13-time Grand Slam champion Roger Federer, Djokovic, Andy Murray and Nikolay Davydenko have clinched their spots for Shanghai, but Davydenko is the only one who has won the Paris tournament, in 2006.
Nadal will hope to go one better than last year, when he was well beaten 6-4, 6-0 by David Nalbandian in the final, while Federer will be hoping to can put an end to his Paris jinx by reaching at least the semifinals for the first time.
Nadal, who already leads the ATP for titles this year, will go for his ninth trophy of the year.
The Spaniard could meet Frenchman Gael Monfils in the third round and Davydenko in the quarters, while Federer opens against either Josselin Ouanna or Robin Soderling - against whom he is 7-0.
Soderling beats Simon to reach Lyon final
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