The Greece striker scored in five European away games last season, including a goal in the 2-1 defeat to Barca in the Nou Camp, and notched both home and away in the first qualifier of the current term - against Northern Irish side Cliftonville.
Samaras warmed up for the visit of the Catalan giants with a hat-trick in a 5-2 Scottish Premiership win over Kilmarnock at Rugby Park on Saturday in a performance described by the Hoops boss as "world class".
"He is hugely influential at times in these European games," said Lennon, when asked about the importance of Samaras.
"He enjoys the arena, he enjoys the challenge that these games bring.
"You all saw on Saturday what a talent he is and when he plays like that he is very difficult to stop.
"I hope that he hasn't peaked too early because I feel that if is to get something out of the game I need Samaras to have a big game.
"In the Nou Camp, before he went off injured, he was causing Barcelona lots of problems and I am hoping for more of the same tonight."
The former Celtic skipper is also looking for a good display by keeper Fraser Forster.
He said: "What you need against Barcelona is a fair amount of luck if you want things to go well way on the night and you need your goalkeeper to play very well.
"And in Fraser Forster I have got one of the best goalkeepers in the competition."
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