We need to improve. I am not going to stand here kidding anybody.Harry Redknapp
Blues lost 1-0 to German outfit 1.FC Union Berlin in Wolfsberg, Austria, in their first pre-season game.
It was Berlin's fifth friendly as they ramp up preparations for the forthcoming 2. Bundesliga campaign.
No matter, Redknapp insists he wants his players to be better.
"It's difficult, it's the first game and they've had a few games and they're a good side," he said.
"But, listen we need to improve. I am not going to stand here kidding anybody.
"Yes, it wasn't easy. We gave everyone a run. But some of the lads have got to do better to convince me to get anywhere near my team."
Redknapp made seven changes at half-time and a further substitution just after Berlin netted the game's only goal, in the 61st minute.
It was always the plan for every available player to get minutes under their belts.
Adams Legzdins played the entire match as David Stockdale (back) and Tomasz Kuszczak (knee) were not quite right.
Stephen Gleeson, who has been on the mend from an ankle issue since Blues reported back for pre-season, was also absent and Cheick Keita has had a sore groin the past couple of days.
Marc Roberts made his Blues debut as a half-time substitute and trialist Ravel Morrison also came on at the break, to play in a role just off Clayton Donaldson, although he began to forage deeper for the ball as the match went on.
Redknapp commented: "He's got good ability.
"He was too deep. He needs to play up the field. If he is going to be the player I know he can be he has got to be up there hurting the opposition. He needs to understand that.
"He is with us for the month, I like him. He has trained well, he has worked hard, he has been very good," added Redknapp, who said that Blues were continuing to make moves in the transfer market.
"We are very active, we are working our socks off, everybody, the owners, myself, trying to bring some players in to improve the quality of the squad.
"We have got plenty of irons in the fire, we are hoping to make some signings in the next week or so."
Blues, meanwhile, gave a short trial to former FC Copenhagen striker Julian Kristoffersen last week at Wast Hills but did not pursue matters any further before they came out to Austria.