Derby boss Phillip Cocu hailed his side's perseverance as they overcame a stubborn Scunthorpe side 1-0 to advance to the second round of the Carabao Cup.
The Dutchman made 11 changes from the weekend draw with Swansea, handing debuts to four players, and the Rams needed a stunning 78th-minute strike from teenager Lee Buchanan to seal a meeting with east midlands rivals Nottingham Forest in the next round.
"This what cups are about – you have to win. I'm happy we did it within the 90 minutes," Cocu said.
"We struggled a bit in the beginning and I was not so happy with how we were positioned on the pitch.
"We couldn't play the game we like to play so after about 25 minutes I changed a few positions and I think it worked better.
"From then on we were more dominant and were creating chances on goal.
"You have to try to find a way to win every game and you can't always do that the way you want to do it – sometimes you have to adjust. The players did well today and we deserved to win."
Scunthorpe were the better side for the opening half an hour, after which the Rams dominated possession.
Just after the restart, in a manic few moments, only a strong hand from Derby goalkeeper Ben Hamer kept out Adam Hammill's deflected strike, while Jamie Paterson was denied by Scunthorpe's Rory Watson after seizing on an under-hit backpass.
Yet just when it began to look like the Iron's resolve might be enough to take the contest to penalties, 18-year-old Buchanan drove into the penalty area from the left and fired high into the far corner on debut.
For Scunthorpe boss Paul Hurst, whose side are bottom of the Football League following a 4-1 defeat at Cheltenham on Saturday, there were positives in defeat.
He said: "I don't like losing any games but there are ways to lose.
"Tonight I felt like we had a real go through some adversity – like not having a centre-forward on the pitch when Lee Novak went off after 25 minutes.
"There were lots of positives for us – we were more organised and gave a couple of lads debuts.
"We couldn't get a goal to take it to penalties but I'm much happier and that was much closer to the work-rate standards we expect moving forward.
"Derby had a lot of the ball and we had to keep our shape and be disciplined. If that's a reaction (to the weekend), great, but really that's what I expect – what any manager would expect."