Emile Heskey's shock equalizer in stoppage time left Chelsea five points behind Manchester United with four games to play.
The former England striker's goal on a volley came in his 400th top-flight appearance. Ghana midfielder Michael Essien had given Chelsea the lead with a 55th-minute shot from the edge of the penalty area.
Manchester United could wrap up the title when it travels to Stamford Bridge on April 26.
Wigan is now six points clear of the relegation zone.