Smith felt his side gave away soft goals in the defeat to Celtic
Rangers manager Walter Smith praised his players for their "fantastic" effort despite losing 3-2 to Celtic.
But he admitted they conceded soft goals with keeper Allan McGregor and the suspended Carlos Cuellar missing and David Weir hobbling off injured.
"I felt it was a decent game but I am a little bit disappointed to give Celtic the goals rather easily," Smith said.
"It was poor defending. That apart, our players did exceptionally well to come back from the early goal."
Scott McDonald opened the scoring for Celtic against the run of play but Weir and then Daniel Cousin gave Rangers the advantage before McDonald drew Celtic level just before the break.
Barry Robson scored what proved to be the winning goal from the penalty spot on 70 minutes after Kirk Broadfoot fouled McDonald in the Rangers box.
Weir limped off in the second-half with a groin strain and Steven Whittaker received a second yellow card in stoppage time for a rash challenge on Shunsuke Nakamura, adding to Smith's injury and suspension woes.
"We are disappointed to lose the last goal, I think it was a contributory factor that Davie Weir had come off," Smith told BBC Radio Scotland.
"With Christian Dailly, Amdy Faye and a new goalkeeper, we had a little bit of disruption in defence."
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