The Scottish champions, guaranteed a Europa League spot after Barcelona beat Spartak 3-0 in Moscow earlier in the evening, will go through if, in their home game against the Russian club in a fortnight, they better the Portuguese side's result in the Nou Camp.
Lennon, who revealed skipper Scott Brown is set to undergo surgery on a hip complaint which could keep him out for 10 weeks, and who will be without midfielder Victor Wanyama for the visit of Spartak after he picked up another booking, said: "I think Benfica are capable of getting a win in Barcelona, for they are an excellent side.
"But we have to make them do that.
"I don't know what kind of mindset Spartak will be in, they might want to spoil our party, we have to be totally focused.
"What we have to do is win at home and make Benfica win in the Nou Camp which is no easy feat.
"No one gave us a prayer coming into this competition, these players have been exceptional, they have made a name for themselves and we are still in with a good chance of qualifying."
Brown has been battling all season with a hip complaint, only playing intermittently and usually in the big games, but had to succumb to the pain in the second half when he was replaced by Kris Commons.
Lennon said: "Scott Brown has run his course, we may have to book him in for surgery.
"We are looking at eight to 10 weeks.
"He has been pushing himself to the limit and we can't keep asking him to put himself through the amount of distress that obviously he was doing towards the end of his time on the pitch.
"He has been a huge player for us this season, I think it is time to get the problem addressed and hopefully he will have something to look forward to in the new year."
Ola John gave the home side the lead in the seventh minute before Georgios Samaras levelled in the 32nd minute from a Charlie Mulgrew corner.
Defender Ezequiel Garay restored Benfica's lead in the 72nd minute to ultimately, and deservedly, leave both sides on seven points after five games.
Benfica coach Jorge Jesus will take succour from Celtic's win over Barcelona at Parkhead earlier in the month, when he takes his side to Spain.
He said: "Now we are playing on the biggest stage in the world against the biggest team in the world.
"But we have shown we are more of a team than Celtic and they beat Barcelona so nothing is impossible."