Head coach Toby Booth made no excuses after London Irish slumped to a 20-19 home defeat at the hands of Edinburgh in the Heineken Cup.
Irish were without six notable performers including Delon Armitage, Topsy Ojo and Jonathan Joseph in a defeat that left them requiring some powerful results during their away ties in Pool Two.
Booth said: "We do have a number of our more potent players missing at the moment, but I am not making an excuse, we didn't play well and will need to play a lot better in Cardiff on Friday night."
Booth also dismissed the influence of losing England centre Shontayne Hape to a yellow card 11 minutes from time, and declined to comment on the elbow Sean Cox appeared to drive into Hape's face after tackling the player to the ground.
"The citing officers will deal with those things, but they are not what cost us," Booth said. "I knew this would prove to be a topsy-turvy pool and this result certainly makes our lives in it more difficult. But if you are going to get things wrong in a pool game, better in the first game than the last.
"We were pretty poor by our standards and we could not control the game the way we usually can. Take nothing away from Edinburgh who were better than us in that area.
"Losing Hape didn't help, it was a call by a touch judge which the referee acted upon. That is beyond our control as coaches. I feel we left too much out there, even though we did have to end the game with 14 men."
Hape's running battle with Cox led to his card after the Irish back shoulder-charged his opponent off the ball. To make matters more annoying for Booth, the resultant penalty proved to be Edinburgh's winner.
"Emotional control is very important out there, but margins are very tight," he said. "If you dive under a player to prevent him scoring a try, to hold him up, and you get it right, you are a hero. But get it a split-second out and it can be a yellow card; tight margins.
"The cards that are coach-killers are the cheap, dull ones that are not part of a competitive contest. And you cannot rely on Tommy Homer to always win games for us. He's a 90% goal-kicker, but we must be able to win games if he misses one kick."