Derbyshire last found the net for Blackburn in the quarter-finals of this competition in December 2008 before joining Olympiacos from Ewood Park.
He returned to England last week and popped up with a poacher's effort to guide Alex McLeish's side to an unconvincing win over their npower League One opponents.
Dale skipper Gary Jones twice found the target in front of a crowd of just 6,431 but goals from Derbyshire, James McFadden and David Murphy proved enough for the Premier League side.
McLeish is keen to tie up a deal for Wigan winger Charles N'Zogbia before Tuesday's deadline, and on this showing at least Blues need to strengthen their squad if they are to repeat last season's ninth-placed finish in the top flight.
Blues made eight changes against the League One side and it showed in a performance often lacking cohesion, quality and drive, particularly during the opening half hour.
Dale strikers Anthony Elding and Chris O'Grady both wasted presentable chances to open the scoring before captain Jones tapped in the opener and the Premier League side were fortunate to be handed a soft penalty just three minutes later.
McFadden converted to level the scores and while the introduction of Sebastian Larsson at the break triggered a much improved display McLeish will not have been happy with the first 45 minutes.
Elding wasted a free header and O'Grady shot wide before the lower league side took a deserved lead in the 25th minute through captain Jones.
Andrew Tutte was the architect down the right, and when his cross was volleyed in by Scott Wiseman, Maik Taylor could only parry the ball into Jones' path for an easy three-yard finish.
Referee Mike Russell then handed the hosts a generous penalty when Derbyshire was sent tumbling by Marcus Holness, and McFadden stroked in the 28th-minute spot kick.
McLeish unsurprisingly made a change at the break, bringing on midfielder Larsson for McFadden and from his corner Murphy put the hosts ahead in the 48th minute.
Larsson swung in a deep delivery which Roger Johnson headed down and the left-back was left with the simple task of volleying home from five yards out.
It was a good way for Murphy to mark his return from 16 months out with a broken kneecap.
Larsson was the creator again five minutes later as Derbyshire fortuitously opened his Blues account.
After another corner from the Swede was only half-cleared, Lee Bowyer's slide rule pass played Larsson in on the right of the area.
He picked out Derbyshire perfectly in the middle but the former England Under-21 man miscued his shot into the midriff of goalkeeper Josh Lillis.
He was lucky to see the ball pop back out, hit him on the ankle and cross the line before a defender could clear.
The quick-fire double appeared to have killed off Dale, who were a shadow of the side who bossed the opening 30 minutes.
But they found a lifeline in the 76th minute when O'Grady powered to the byline before coolly picking out Jones for a side-foot finish.
Blues held on for the win and those fans who did turn out were treated to a promising debut from 16-year-old substitute Nathan Redmond - the club's youngest debutant since Trevor Francis.