The club's zonal system during corners and free kicks has been criticized in recent weeks, but the Italian manager believes his players would crumble under a different setup
Steven Caulker gave Tottenham the lead by heading home a free kick in the defending champions' 2-1 victory at the Etihad Stadium on Sunday afternoon.
Poor defending in dead-ball situations has plagued Mancini's side this season, but despite criticism for their zonal setup the Italian coach thinks the team would fare even worse if it changed systems.
"We are not strong enough to mark man-to-man, and every time we do there is a risk of conceding a penalty," Mancini told reporters.
"If we work, we can improve the system. We have let in goals because of it, but we can change that. We are working on it, but we need to work more."
Despite its fairly mixed performances so far in 2011-12, City remains unbeaten in the Premier League and trail league leaders Manchester United by just two points.
Mancini admitted that he did not understand the concerns about his side's form so far this season, claiming that the club's poor results was often a consequence of bad luck or its own mistakes.
"We have made some bad mistakes in the Champions League, have had some bad luck, and have sometimes played a bad game," he said. "But we don't have a bad problem as some people like to say."