The Italy No1 was again outstanding in Juve's Champions League win over Maccabi Haifa, but Trezeguet says it's a worrying trend.
He explained: "It was a difficult game and we are happy with the points, but there is a lot of work to be done, both in attack and defence, to find the right balance.
"Our Man of the Match was once again Buffon. On the one side it is positive to have the best goalkeeper in the world, on the other obviously that's a bad sign and shows we need to improve a lot.
"We are trying some new tactical systems to find the option that is most suitable to these players."