The attacking midfielder scored twice to put the Giallorossi two goals to the good on Sunday, but the visitors came back to emerge victorious - much to the Argentine's fury
The former River Plate man gave his side a commanding two-goal cushion in the first half but the Friuliani responded with a Maurizio Domizzi strike and a double from Antonio Di Natale in the second half to stun the capital outfit.
It was not the first time that the Giallorossi have thrown away winning positions this season, and Lamela admits that he is mystified by their tendency to leak goals, as he highlighted their extensive work on the training pitch.
"We are angry. I don't understand the reasons for this defeat," Lamela told La Gazzetta dello Sport.
"In the future, we must continue to work with the right spirit. We are working hard in training during the week. It's very strange that on the pitch we are not producing the right results.
"Five goals? With Zeman as coach, I'm very happy with him and also my colleagues, who helped me score."