Taarabt, only recently arrived at San Siro on loan from QPR, was making his Champions League debut and was one of the positives for Milan as they dominated possession but failed to beat Atletico goalkeeper Thibaut Courtois.
The Italian giants wasted a number of good opportunities before they were punished when Diego Costa headed home at the back post with seven minutes to play, but Taarabt is confident they can pick up the result they need in the second leg.
"Is it finished? No, I don't think so," he told Sky Sport Italia. "We put in a great performance, tactically almost perfect, and we were just unlucky on the incidents.
"In the second half we ran out of energy a little bit and should have scored a goal.
"Now we know it is going to be very difficult, but we are going there to score."
The 24-year-old, who has joined Milan until the end of the season, was pleased with his own display and hopes to maintain that form under new head coach Clarence Seedorf.
"I arrived from a different league and am very happy to be playing for Milan," he added. "The coach put a lot of faith in me and I scored straight away against Napoli (in Serie A).
"I think my performances have been good, but it's just a shame about the result."
