"It wasn't inspired, it was enforced. Dean has been off all week with a bug and we didn't think he would last the game.
"He felt a bit rough before the game and at half time but we asked him to give us a shout when he couldn't do any more which he did with 15 minutes to go."
Doncaster had won at Pride Park in December but Clough reckoned the difference this time was his team's defensive toughness.
"We didn't give a goal away today which we had in the previous home games. If you go into the last five or 10 minutes at 0-0, you've got a chance of nicking it and we gave ourselves that chance.
"If our decision making in the final third had been a bit better, we would probably have got something a bit earlier.
"We want to improve in the league and try and get to halfway and we can do that in tandem with a cup run as well."
Doncaster boss Sean O'Driscoll was philosophical at his team's exit.
"It was disappointing to lose a goal at the death and I thought we were well worth a draw but that's football.
"It was a great strike by Jay McEveley. I tell our players if you don't shoot you don't score so you've got to give him some credit for taking responsibility.
"We had a difficult game on Tuesday (at Brentford) on a quagmire of a pitch so I thought we handled the situation really well. We were a little bit tired but we didn't use that as an excuse.
"I thought Tuesday night was a test of their attitude and they came through with flying colours. This was a test of their resolve and regardless of the result, I thought they were first-class.
"The only certainty in football is that things don't go your way and it's what you do next that's important.
"There's no point moaning and groaning as a manager, coach or player, you just have to get on with it and we've done that really well in the last two games which augurs well for the future."
Doncaster had won their last three games against Derby and they had a chance to take the lead in the 22nd minute of an open contest.
John Oster picked the ball up near the left edge of the Derby penalty area and the home defence opened up in front of him but he elected to pass instead of shooting and the ball went out.
Billy Sharp made himself some space but could not get enough power in a low drive to test Stephen Bywater and Derby did not create a chance until near the end of the first half.
Steven Davies played a clever ball through the middle of Doncaster's defence but Neil Sullivan reacted swiftly to save at Stephen Pearson's feet.
Both teams created openings in the second half without finding a telling finish as Sharp twice went close and Davies headed over and then shot wide.
Derby almost broke through in the 82nd minute when Pearson crossed and Kris Commons looked certain to score but Sam Hird twice got his body in the way.
But there was nothing the visitors could do about the goal that settled the tie in the 88th minute.
Pearson again broke down the left and although his shot was charged down, McEveley lashed the rebound into the top corner from 25 yards.