Lazio boss Simone Inzaghi urged calm after 2-1 Europa League defeat to FC Cluj.
Lazio had the lead through Bastos, but eventually were overrun.
“Without doubt, as is often the case, we deserved more and it's a very disappointing result," Inzaghi told Sky Sport Italia.
“It was above all an excellent first half performance. I am convinced we will go through to the next round and we must always believe in what we're doing. We should've finished the game earlier.
“It's also fair to say the referee should not have awarded that penalty. If we'd gone 2-0 up, we would not have had these issues. We've got to keep our heads up, as on Sunday there is an important game against Parma.
“These two defeats with Cluj and SPAL are very disappointing, because we need to be more effective in attack and kill games off when we're in control.
“We have to analyse why we keep running out of steam in the second half. This was basically a photocopy of the match against SPAL, despite the fact we've worked on those errors over the last three days."