Ridgewell played at left-back in Saturday's hard-fought 2-2 draw in their Premier League opener at Sunderland.
But the Londoner wants new faces added to the summer recruitment of goalkeeper Ben Foster and strikers Nikola Zigic and Matt Derbyshire if Blues are to prosper this season.
"We need to make the squad a bit bigger and get some more quality," he told the Birmingham Mail. "Everyone wants to take the club forward. We want better players, we want a better side.
"Hopefully the owner and the chairman can back the gaffer in the players he wants to buy and we can get them in before the window closes."