Nicky Law praised the peak fitness of his "elder statesmen" as City's sixth away win of the season buried any lingering relegation fears.
A late goal scrambled in off Derby defender Pablo Mills earned Law's side a 2-1 victory at Pride Park and lifted them up a place to 18th.
City are now within striking distance of a clutch of clubs in mid-table and Law said: "The players deserve everything they get. They've worked tirelessly to stay where they are.
"They have come in for a fair bit of criticism this year and I don't think everybody has realised quite how difficult it has been. But to a man they've stuck at it and hopefully now they can go on and get their rewards.
"The fitness of the lads here is fantastic and we could have hung on comfortably for another 20 minutes. We've got some elder statesmen, the likes of Ashley Ward, David Wetherall, Peter Atherton and Jamie Lawrence, who are all super fit.
"That showed with the winning goal where we've got from one end to the other and all gone piling in the box. The fitness levels and desire of the players is magnificent."
The winner was initially given to Jamie Lawrence and then Ashley Ward but television replays clearly showed it went in off Derby's teenage centre-half Mills.
Law added: "It could have gone anywhere but you tilt the luck your way some days. Wardy claimed it although whether it was off him I'm not too sure.
"But he has worked very hard up there and you make your own luck."
Andy Myers is a fresh injury doubt after limping off with a slight thigh strain.
Wayne Jacobs, who replaced him from the bench, is set to step in for tomorrow night's home game against bottom club Sheffield Wednesday.
Law said: "Andy started to feel it towards the end so we got him off quickly. Hopefully we've caught it early enough.
"But we do have competition for places in the squad now, which has not been the case for most of the season."
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