"I don't know [how many teams are in the title race] - more than two certainly," said Wenger.
"[Chelsea's defeat] just confirms that it's difficult for everybody to win the game, that there is no difference between the teams now.
"The teams are well organised, they are physically very strong and if you're not at your best, you don't win the game. It's the same for everybody.
"Manchester [United are] top of the league, but they've already lost three games so I believe that the Premier League is very competitive."