Alex McLeish pinpointed striker Chucho Benitez's return to form as the key factor in Blues' 2-1 win at Portsmouth last night.
The Ecuadorian hitman, starting his first match in four weeks, fed strike partner Cameron Jerome for both his first-half goals and terrorised the Pompey defence which had looked so untroubled on Saturday in the Cup.
"I thought Chucho had lost a bit of confidence in the last few weeks. He had an injury and perhaps wasn't feeling quite his best," McLeish explained.
"The players were finding it difficult to find him on the pitch and he wasn't getting into any of the little pockets he had been looking dangerous in during the early part of the season.
"He came on last Saturday and I think he got a wee lift from his performance. He created a bit and he looked very dangerous tonight."