Como, newly promoted to Serie A this season, led after an early own-goal by Nicolo Casale and a second-half right-footed finish by Patrick Cutrone from the edge of the box. But late strikes by Santiago Castro and Samuel Iling-Junior rescued visitors Bologna.
"We had an important chance to win... we were solid, but we have to be better at closing it out," Fabregas told reporters.
"We are lacking in this, we have to work and improve on this."
Como, who have two points after four matches, will visit Europa League champions Atalanta on Sept. 23.
"I have to do more to help the boys be more nasty in front of (the) goal and close out the game. But now let's think about Atalanta and how to deal with this very difficult match," Fabregas said.