Fonseca spoke ahead of their match against Empoli.
He said: “We were better organized against Juve, we were better in transition against Slovan.
“It seems that when we improve something, other problems arise. Just because you win doesn't mean we can close our eyes and pretend everything is fine. We have to look at the problems.
“Problems arise game after game. We were well disciplined and worked hard against Juve, while in Bratislava we were a better team in transition. We've always talked about defensive issues, but we have the fifth-best defense in the league. We have admitted the same as Inter and Lazio.
“In Italy you need two faces in attack. We had one against Juve and Slovan, we need one more when we face Empoli and Atalanta.”
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