Thatcher's last game for The Addicks was the 4-0 win against West Ham United and his knee complaint has seen him miss the crucial wins against Newcastle and last Saturday's late 1-0 win against relegation rivals Wigan.
Thatcher is now ready to return and his first game back is against former club Man City, who he signed for Charlton from in January for £500,000.
That means Talal El Karkouri, Hermann Hreidarrson and Souleymane Diawara will fight for the two central defender positions for the pay-per-view outing in Eastlands.