But the Parkhead playmaker also insisted his team-mates haven't thrown in the towel, although they will require something extraordinary when they travel to Turin in three weeks time.
Neil Lennon's players were aiming to make history by becoming the first Scottish club to quality for the last eight of the competition, but those dreams were badly dented when they went down against the Italians.
Commons was disappointed by blunders that gifted Juventus their first and third goals on a night to forget for the SPL champions.
And although he knows Celtic now need a minor miracle in Italy, he says they can't do anything but give it their best shot when they try to rescue the tie.
He said: "At 1-0 and even 2-0 you have a chance but losing a third goal makes it so much more difficult for us. Is it over? We can't accept it is. We all know it is going to be a huge ask now but we've got to go over to Italy and give it our best shot.
"If we score an early goal then who knows? That is the way we must look at it. But they are a quality side and I don't think you'll find they have lost many matches at home by three or four goals, especially in Europe."
Commons, however, reckons the outcome of the game could have been different had Celtic enjoyed a bit of luck in front of goal.
He said: "We had quite a few shots from in and around the edge of the penalty area in the first half and I had an effort which just went wide of the target. We came close on a few occasions but we just didn't get the luck.
"I don't think we deserved to lose 3-0. It is a sore one to take because we played very well in the first-half after conceding an early goal and we started well in the second half as well. It's just extremely disappointing the way it turned out."