The Scottish champions have their UEFA Champions League dreams hanging by a thread after going down 3-0 in the first leg of their last 16 tie with Juventus.
Efe Ambrose was at fault for Juventus' opener, allowing Alessando Matri to go clear on goal to score after just three minutes and the Nigerian again did not cover himself in the glory with the third goal from Mirko Vucinic.
Asked if the scoreline flattered Juventus, Commons told Sky Sports News: I think so. But if you give top teams opportunities to shoot at goal then you know they are duly obliged to roll it in the back of the net.
"Defensive errors and individual mistakes cost us tonight."
Commons admitted the concession of the early goal stunned the home side and that Juventus punished them late on as Celtic threw everything into attack in a bid to get back into the game.
"It was so early it was a bit of shock to the system, but we rallied and we played some really good football," he said.
"We played at a good tempo and put Buffon under quite a lot of pressure. We just needed one to hit the back of the net. The longer the game went on without us hitting the back of the net, we needed to start advancing our more defensive players and that obviously created gaps and they exploited that."
Celtic boss Neil Lennon blasted Juventus' tactics when defending corners, feeling the referee should have punished their players for grappling and holding inside the penalty area.
"I was usually the man taking the corners but there was a lot of argy-bargy," noted Commons.
"But we watched plenty of the videos that they seem to play within the rules of the game unless the officials deem fit to give us a penalty. There was a lot of holding, a lot of grabbing, a lot pushing, but that's professional football at the top level. There's enough officials nowadays behind the goal, in and around the goal, on the touchline that need to be aware of what sort of tactics they are employing on our players."
Commons is refusing to concede defeat in the tie despite the uphill task facing them in Turin, admitting they must cut out all individual mistakes if they are to have any chance of pulling off an unlikely comeback.
"We need to eradicate the sort of silly errors that individuals made to have any sort of chance in Turin, but you never know get and early and we will see," he said.
"We have got a glimmer [of a chance], but it is going to be a massive, massive challenge. They are no pushovers and they will be thinking the tie is over so that might give us a little bit of an edge."