Robbie Savage says substitutes Jack Grealish and Jordan Ayew changed the game for Aston Villa.
Robbie Savage has told The BBC that Aston Villa's substitutes were the game changers against Birmingham City.
Villa were desperately poor in the first half in the Capital One Cup clash against their rivals, and it was after the second half changes they began to improve, with Rudy Gestede scoring the winner.
Savage singled out Jordan Ayew and Jack Grealish as the difference makers, despite neither scoring, and Gestede netting from a Jordan Amavi cross.
He said: "The two substitutes Ayew and Grealish have been the difference. Well done Tim Sherwood - those two substitutions have won the game for Aston Villa.
"I think this could galvanise Villa's season."
Savage also commented that Sherwood had taken stick for his substitutions in Villa's weekend loss to West Bromwich Albion, and resultantly deserved praise for getting it right this time around.
Villa had 17 attempts on goal to Birmingham City's seven, but only three to two in terms of shots on target.
Pressure was beginning to grow on Sherwood after a poor start to the season, and the win was more a necessity than a great success, but as Savage points out, this could become the catalyst for improvement, with an even more heavily critiqued Liverpool side up next.