The Scottish Premiership outfit were thrashed 6-1 by Barcelona in the Champions League on Wednesday night, and Commons was disappointed by his side's desire during a one-sided second half at Camp Nou.
The 30-year-old told BBC Sport: "We need to rebuild for next year because the target is to qualify for the Champions League again. We need to have a long look at ourselves and get back in to training.
"Once those couple of goals went in before half time, we started to lose our shape and became a little bit disjointed.
"We lost that fight, that desire to stop them putting balls in the back of our net and that's something that we haven't struggled with in the last 18 months in this competition."
Despite their poor performance in Europe, Celtic are seven points clear at the top of their domestic league table.