The Hoops midfielder is not oblivious to the irony of speaking about how to win against Barcelona just a few days after you lost to Morton.
However, the ridiculous highs and lows which constitute the vagaries of the game are nothing new to anyone at Parkhead.
"That's the nature of the business playing in Scotland," said Commons, philosophically.
"We look to win every game - even when we went to the San Siro, we tried to win it.
"If you approach games where you take the foot off the pedal and try to defend for 90 minutes, you end up conceding in 10 minutes and the game plan is out the window. You might as well go into every game thinking you can win."
Of course, it was a different approach when Barca last came to Glasgow, had the lion's share of possession, then conceded goals to Victor Wanyama and Tony Watt.
Memories of how their game plan worked to such great effect back in November is all Neil Lennon's men need to convince them they can enjoy such a dramatic fluctuation in fortunes in the space of just a week.
First of all, though, each and every player must use today's lunch-time kick-off at Kilmarnock to convince their boss they are back on form and worthy of a place in the side for their second Group H game.
"It was unacceptable and bordering on embarrassing that we were beaten by a team like Morton when we've got Champions League and international players in our squad," reflected Commons.
"We'll be looking for a reaction. The manager has already said, if you are not quite at it today, there will be doubt whether you will be ready for Tuesday.
"We've got to go into the game with plan A and make sure we turn them over nice and early."
Key to that will be to find the net, which they failed to do against Morton - despite 29 attempts.
Commons concedes that, against Barca, they will probably get just two or three scoring opportunities, so must be clinical.
Already this season, Shakhtar Karagandy and Elfsbrog have joined Morton in keeping a clean sheet against the Hoops.
So, with leading scorer for the past three years, Gary Hooper, gone, is Commons confident they can get goals on Tuesday?
"Yes, but the difficult thing is going to be getting the ball back off them," he responded.
"You're possibly playing against the best attacking team the world of football has ever seen.
"You have to be mentally tuned in to your defensive duties - the entire team, not just the back four.
"If we do get a chance or two, we really must take them."
The former Scotland cap is joint top scorer with Anthony Stokes this season on four, and has faith in the men trying to fill Hooper's boots.
He said: "Gary's one of the best strikers I've ever played with, so he is going to be hard to replace.
"But the things Teemu Pukki has been showing in training, there is no doubt he can fill his shoes.
"It's just about him getting game-sharp and then being ready for these big games.
"When he finds his feet, I hope he will be just as clinical as Gary was."
Commons is entitled to point out the victory over Barca last November was achieved without the then- injured Hooper.
Pukki is about to be judged against some of the very best in the business as Lionel Messi, Naymar and Co. prepare to set their sights on Fraser Forster's goal.
Commons is more excited than worried by the prospect of facing this partnership and said: "It's not impossible to stop them - they don't score every game, do they? Almost!
"You have to take it as a challenge and not be daunted by it.
"They will know coming to Celtic Park is going to be a difficult task for them to get goals.
"I don't think they will underestimate us. They know what we are capable of."
Celtic reminded everyone against Milan, even though they lost two late goals, a result which, allied to Barca's 4-0 demolition of Ajax the same night, leaves Group H looking the way most expected.
However, Commons is more interested in getting their first point or points on the board to kick start their push for the last 16.
Commons would regard that as more of an achievement than winning a treble, simply because they are expected to win every domestic competition they enter.
But if they are to avoid being left with a mountain to climb in the group, that perfect game must be delivered on Tuesday.