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.
"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."
Celtic famously beat Barcelona 2-1 in the group stages last season on their way to the last-16 but lost 2-0 to AC Milan in their opening game of this season's campaign at San Siro.
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."