The Bhoys scored just three goals in the six group stage matches of the Champions League this season, as opposed to nine last term, which saw them through to the Round of 16.
Wednesday night's 6-1 defeat at Barcelona was the conclusion of a fairly poor campaign in Europe's top competition for the Scottish champions and midfielder Commons suggests their shortcomings come down to not having a quality goalscorer like Hooper who joined Norwich City in the summer.
"I think when you are relying on people, midfield quality to get you goals then once they dry up you are looking for a striker," he said.
"In a Celtic team you are looking for a striker to get between 20 and 30 goals a season and at the minute we haven't quite got that.
"I know people are working hard on and off the field to try and get us the goals but replacing someone like Gary Hooper is going to cost you between six and 10 million and, at the minute, we are not willing to spend that."
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