The striker returned to England this week with Birmingham after agreeing a season-long loan from Olympiacos.
Derbyshire moved to Greece in January 2009 after becoming frustrated with his lack of first-team opportunities at Blackburn, the club he joined as a 17-year-old.
And it is Rovers who will provide the opposition for Derbyshire at St Andrew's on Saturday as Birmingham look to continue an unbeaten home record that stretches back to last September.
Blues boss Alex McLeish has already said the 24-year-old will play some part in the match, his first in the English top flight since a 2-2 draw for Blackburn against Manchester City in December 2008.
Derbyshire said: "For me, it's more important to put a Birmingham jersey on and go out do the best I can for Birmingham City, whether it's against Blackburn or anybody else.
"I believe I was quite successful at Blackburn in the games I played. I had a fantastic time at Blackburn, it's a nice club, the club I supported as a boy.
"It will be strange, of course, because I know most of the players and they know me but you've got to put it behind you and concentrate on winning the game for Birmingham."
Derbyshire's move to Olympiacos, initially on loan, was one of the more surprising transfers of recent years.
But he adapted to Greek football impressively and was named man of the match in the Greek Cup final against AEK Athens after netting twice.
That prompted Olympiacos to shell out £3million for Derbyshire last summer and he continued to find the net fairly regularly, earning the nickname 'The English Killer' after scoring the winner against bitter rivals Panathinaikos.
Derbyshire said: "The first two or three months was quite difficult with the language barrier. You don't know anybody, you don't know the place, you know nothing.
"And trying to learn the Greek language, which is very difficult. But when I got playing and started to do well, everything started to click in place.
"I had a great experience, a great time there. I'd never go back on it. If I had the same time again and it was Olympiacos or Blackburn I would do the same because I got to play Champions League football.
"But I'm delighted I'm back in the Premier League with Birmingham."
The Greek league is not seen as one of the strongest in Europe but Derbyshire believes it will prove a good grounding for his return to England.
"For anyone who's ever managed to watch a Greek game, it's filled with passion and enthusiasm and everything beyond that," he said.
"The Premier League's fast and furious whereas the Greek league isn't as fast and furious but the Greek league is very competitive and very technical."
Derbyshire burst onto the scene with three goals in four games for Blackburn in January 2007 and seemed set for a bright future at Ewood Park.
But he continued to be used mostly as a substitute and the chance to try his luck in a different league proved too good an opportunity to turn down.
Derbyshire feels he returns to the Premier League a better player and is confident there is still more to come.
He said: "I'm only 24. I've been out of the Premier League for a while but while I've been away I've learned a lot and hopefully I can push on for the team."
And one thing the striker certainly will not miss is the Greek weather.
"Not at all," he added. "It's way too hot for me."