Gallas, who signed a four-year deal with Arsenal in 2006 having helped Chelsea to back-to-back Premier League titles under Jose Mourinho, was responding to his former manager's comments regarding the future of Gunners star Alexis Sanchez.
Wenger stressed that he was not concerned about recent speculation linking the Chile international with a move to Stamford Bridge because “There is only one team in London".
Gallas, however, who spent 12 years playing in the capital, does not agree.
“The biggest team is Chelsea,” Gallas told talkSPORT. “They are top of the league and maybe they will win the league.
Gallas, who left Arsenal to join north London rivals Tottenham before ending his professional career in Australia with Perth Glory, failed to win a single trophy during his four-season stay at the Emirates, but claimed four at Stamford Bridge.