They already trailed to a 22nd minute goal by SimoneTiribocchi and looked set for another defeat until substitute Ronaldinho scored six minutes from time to ease some of the pressure on coach Leonardo.
But Jose Mourinho's men were down to 10-men just after the hour as midfielder Wesley Sneijder went for two bookable offences and Atalanta capitalized with an equalizer by substitute SimoneTiribocchi on 81 minutes.