The Greece striker's performance in the Scottish Premiership win over Killie was described as "world class" by manager Neil Lennon.
Samaras, 28, was reluctant to accept his coach's accolade and claimed there was no need for a boost ahead of the Group H clash with the Catalan giants, who will be without Lionel Messi after he limped off out of Saturday night's 2-0 win over Almeria with a thigh injury after scoring his side's opener.
"We always believe in the ourselves and our team. We don't need to beat Kilmarnock 5-2 to go and be competitive against Barcelona.
"I feel good within myself. I don't need any confidence. I believe in myself every hour and every day.
"I know exactly what I can do for this team and to help my team-mates win games."
Samaras, however, insists the Scottish champions will go into the Barca match with the same attitude they took to Italy.
"We will go and enjoy it," he said. "We were a bit unlucky in that game against AC Milan, we didn't take our chances.
"I don't think we will have so many chances against Barcelona so we need to be more clinical.
"If we have the chance, we need to put it in the back of the net if we want something good from the game, like we did last year.
"We have to stay focused, try to minimise our mistakes and try to play to our strengths."
After Kris Commons capitalised on a mistake by Killie goalkeeper Craig Samson to give the Hoops the lead in the 19th minute, Samaras scored twice, both with well-taken shots, to give the visitors an apparently unassailable lead.
However, Kilmarnock midfielder Sammy Clingan reduced the deficit with a great free-kick before defender Sean Clohessy made it 3-2 just before the break.
The home side, though, did not really threaten in the second half and Samaras sealed the win in the 87th minute with a header before substitute Amido Balde, on for Teemu Pukki, scored a fifth two minutes later.
Killie boss Allan Johnston, still looking for his first win of the season, said: "We were well on top for the first 20 minutes but made a mistake and were punished for it.
-"But it was a great comeback from the lads, it shows the spirit they have and the quality of players we have got.
"We were in the game until 10 minutes to go. There was a lot of positives, we just need to cut out the mistakes.
"If we keep that level of performances up, we wont be far away and we will start winning games."