Manuel Pellegrini admitted conceding two goals to Viktoria Plzen is a concern for Manchester City.
The Eastlands club beat the Czech outfit 4-2 at the Etihad Stadium in the Champions League on Wednesday night, making it the fourth straight European match in which they have failed to keep a clean sheet.
City twice squandered leads against Plzen before eventually overrunning the visitors and Pellegrini indicated it was a slight negative for his team especially after letting in goals against CSKA Moscow twice (5-2 win and 2-1 win) and Bayern Munich in the 3-1 loss in October.
"When our team concedes goals it is always a concern as it is something we are not doing well," he told Sky Sports.
"They scored and had two or three more chances and the last game with CSKA too, but we must continue improving in that sense."
