In a never-to-be-forgotten night in the east end of Glasgow last November, Neil Lennon's side beat the Catalan giants 2-1 in their group match on their way to the last-16 of the competition.
Celtic played well only to lose 2-0 to AC Milan in the San Siro on match day one of this season's Group H campaign which encouraged the Hoops midfielder, who shrugged off the shock 1-0 defeat by Morton in the Scottish League Cup third-round on Tuesday night.
Ahead of the Scottish Premiership clash with Kilmarnock at Rugby Park on Saturday, Commons was asked what were the chances of another unlikely win over Barca.
He said: "It is going to be difficult but I think it will be very unprofessional of them if they didn't think that we were a threat.
"I know we got beat by Morton the other night but they will be looking at footage of us playing against AC Milan and how well we did there and probably showing our own strengths and weaknesses.
"They obviously now have Neymar who is one of the best players in the world so attacking wise, they will be a bigger threat (this year).
"But for us, it is about staying focused and trying to repeat what we did last year.
"We certainly got some lady luck last year so we will be looking for a bit more of that."
Commons accepts the Hoops' game plan against Barcelona will probably involve the unusual sight at Parkhead of Celtic on the back foot for most of the game.
"You have to give Barcelona respect," he said.
"Even against the best teams in the world they probably have 65 to 70 per cent of possession so you have to accept that they have technical geniuses throughout the team.
"If you start being a little bit kamikaze and chasing the ball around you will end up getting picked off and the ball is in the back of the net before you know it."
The former Derby and Nottingham Forest player, though, believes that the Hoops squad is stronger this season despite the loss of defender Kelvin Wilson, midfielder Victor Wanyama and striker Gary Hooper, among other fringe players, during the summer.
Lennon recruited Virgil van Dijk, Steven Mouyokolo, Derk Boerrigter, Amido Balde, Teemu Pukki and Nir Biton, all of whom Commons believes will make Celtic stronger when they have adjusted to life at Parkhead.
He said: "We have lost three of our better players, without a doubt - Kelvin, Victor and Gary, along with other squad members.
"It is a bit of a transition period for us at the minute because we have bought players in at the last minute like Teemu Pukki, Amido Balde and players who came in and got injured (Steven Mouyokolo).
"So we are thin on the bones but if the new additions to the squad find their feet pretty sharpish I think we will have a better squad than last year.
"It just takes that little bit of time to bed in.
"When you bring in foreigners, there is always the language barrier and culture and getting used to playing in front of such passionate fans.
"So it is going to take a little bit of time but not as much as people might think."
Lennon will make changes for the trip to Rugby Park but warned his players that anyone keeping themselves for Barcelona will be in trouble.
He said: "I will not make wholesale changes but Commons, (Anthony) Stokes, (Georgios) Samaras, (Emilio) Izaguirre will come back into contention, players who have been playing on a regular basis since the start of the season
"But if anyone has an eye on Tuesday going into the game tomorrow and it manifests itself on the pitch, then they won't play (against Barca).
"This game is very important to the league and off the back of Tuesday night there is even more significance on the game and so they have to play to put themselves in contention for Tuesday night.
"I haven't given Barcelona much thought with the games we have had, we will concentrate on all that after tomorrow."