Davies was forced off in the 72nd minute with an ankle injury, having had treatment on it a short while earlier.
He missed last month’s win over Blackburn with an ankle complaint and it could well be the same injury has flared up.
Jordan Storey replaced him in the back four, this only his second time on the pitch in Championship action this season.
The former Exeter man will be on alert to start at Hull if Davies does not make it.
North End manager Alex Neil said: “It’s his ankle and I’m not sure the extent of it yet.
“We will have to assess it and take things from there.”
The enforced substitution prevented Neil making a last throw of the dice in an attacking sense at Pride Park.
Neil had David Nugent ready to come on for Daniel Johnson but the striker did not get the chance to face his former club.
His two other subs had been made at half-time, with Paul Gallagher and Billy Bodin replacing Darnell Fisher and Jayden Stockley.
Said Neil: “We had 20 minutes left, I was going to take DJ off, move Sean Maguire behind Nuge and try to force the issue.
“Unfortunately Ben pulled up right before that and we had to change the plans.”
Neil offered no excuses for the 1-0 defeat to the Rams, Martyn Waghorn’s 33rd-minute goal settling it.
Derby had plenty of chances to put the game to bed by half-time but only had the slender lead to fall back on.
North End were better in the second half, helped by the double substitution and the reshuffle that caused.
Neil will now look for a good response at the KCOM Stadium on Wednesday,
Said Neil: “At half-time it would have been easy to start shouting and bawling, saying how poor they had been.
“What we needed to do at half-time was fix it and I thought we did that.
“But we didn’t get the goal we needed, which obviously was frustrating.
“Nothing is won at the moment, we are going to lose games on the way.
“What we have to do is take the disappointment from the game and try to make amends for the next one.
“The players know and understand they didn’t play well, they are frustrated themselves.
“We win and we lose as a team, sometimes I will get it wrong and sometimes they won’t perform well. That is part and parcel of it.
“For all the chances Derby created, it took a corner for them to score. That is disappointing because we normally defend them well.”