The Belarus winger joined Blues on a season-long loan from Barcelona this summer but his three league starts so far have brought only one point.
Hleb's most recent appearance, in the 2-0 defeat by Everton on Saturday, saw Birmingham's year-long unbeaten run at St Andrew's come to an end.
The 29-year-old told the club's official website: "I don't know what has been lacking, it's difficult to explain, but this is just football and we need to be positive.
"We need to give a little bit more but I can feel it coming, hopefully it will in the next game. This team are training fantastic and we need to bring that into the games.
"If Blues are to end their poor run at the first opportunity, they will have to beat Arsenal, Hleb's former club, at the Emirates Stadium.
He added: "It will be very special for me, Arsenal are a fantastic team but we will still try to take maximum points."