
The five-times European champions, runners-up last summer, have just one point from three games and now need to win their remaining three matches to stand a chance of advancing.
But with two of those matches at home, the Spaniard said he had not given up hope.
"Obviously it is very difficult now for us to get through but I believe we still can," he said. "There are three games left and we must win all three, but we can do that.
"We have to wait to see now what we must do, how the numbers add up. The fact that Porto drew with Marseille in the other group game was a help for us, it certainly improves our options."
"If we continue to play like we did in this match, with so much dominance, we have a chance."
Marseille sit top of the group on seven points, two more than Porto.
Liverpool play Besiktas in their next game at Anfield on November 6 and then take on Porto at home before travelling to Marseille for the final group match in December.
"I do not see this as a test for me as a manager, this is football, if you keep doing the right things like we did here, we will achieve what we want," Benitez said.
DPA