Rui Vitoria criticised Benfica's wastefulness after a staggering Besiktas comeback saw them miss the chance to seal a place in the Champions League last 16.
Benfica squandered a three-goal advantage as they capitulated, with Vincent Aboubakar providing the final blow in the closing stages of an enthralling fixture to haul the teams level at 3-3.
Goals from Goncalo Guedes, Nelson Semedo and Ljubomir Fejsa in the first half looked like sending the Portuguese champions on their way to progression from Group B.
However, second-half goals from Cenk Tosun, Ricardo Quaresma and Aboubakar saw the home side claim a point in what was a brilliant response.
Napoli's draw with Dynamo Kiev later on Wednesday means the Serie A side are level on points at the top of the group with Benfica on eight apiece, with Besiktas one back.
"The first half was fantastic and in the second we had chances to kill off the game, but we didn't get the fourth goal and handed them a way back with some lapses," said Benfica coach Vitoria.
"It leaves a bitter taste that this draw means everything hangs on the final game.
"We knew it would be complicated. We started off very strong and, just as we managed to score three, they also managed to net three after a good second half.
"We're still depend on ourselves. Now we must think about beating Napoli so as to advance to the next phase."
Guedes, who opened the scoring for Benfica, rued his team's inability to see out the game.
"We did everything we could to win," he told reporters. "It is going to be a difficult match against Napoli, but we are counting on the fans to help us win."