The striker is concerned with how the Bianconeri are not being dominant from the start, while coach Antonio Conte praised his side's fight to win 2-1
The Serie A champions surrendered the lead in the fourth successive game on Wednesday as they beat Chievo 2-1 at the Stadio Marc'Antonio Bentegodi, moving up to third in the Serie A table, two points behind leaders Roma.
Cyril Thereau opened the scoring in the 28th minute for the hosts, following a mistake from Gianluigi Buffon, before Quagliarella equalised a minute into the second half with a scrappy effort.
Alessandro Bernardini put through his own net on 65 minutes to hand Antonio Conte's men the win, but the Italy international remains wary that his side keep leaving themselves a mountain to climb.
"We can't keep letting our opponents take the lead," Quagliarella told the Bianconeri's official website.
"It's not a good sign. The coach drummed it into us during the week. It's something that needs to be worked on, even if up until now we've had the character to come back."
Conte praised Wednesday's opponents but went on to laud the fighting qualities shown by his players to recover from the dent of going behind in the first half.
"Hats off to Chievo, they were very organised," the Turin-based club coach said. "We did well to prevent them from breaking on the counterattack, but going forward - especially in the first half - we attacked with very few players.
"That’s something that can happen though, it’s our fourth consecutive game, the sixth for those who played in the international fixtures, and we've rotated many players.
"We know it's a tough league and we'll need to fight in every game to gain a result. To lift our heads and overturn the deficit as we've done in the last two games shows we have important qualities."