Macaulay Gillesphey’s own goal and Bobby Clark’s second-half strike made it back-to-back away wins for the Rams despite a goal for the hosts from Tyreece Campbell and a late red card for Matt Clarke.

It was Derby’s seventh victory on the road this season, and their first in the capital since 2021, and left them only two points shy of the top six.

“I’m very pleased. I thought the effort the group put in was superb,” said Eustace.

“It’s a long, relentless season so it’s really pleasing to see how the group has matured and if you do the right things you get the rewards. We just want to be competitive and see where that takes us.”

Derby went ahead in the 17th minute when Patrick Agyemang reached the byline and drilled in a low cross which Addicks defender Gillesphey could only divert into his own net.

The second goal arrived on the hour when former Liverpool youngster Clark latched on to a neat Ben Brereton-Diaz through-ball and finished past Thomas  Kaminski.

Charlton pulled one back when Campbell, their liveliest player on the night, curled home from the edge of the box.

Derby’s preparations were hindered in the warm-up with goalkeeper Jacob Widell Zetterstrom pulling out of the team 25 minutes before kick-off with a virus.

Much-travelled veteran Richard O’Donnell was promoted from the bench for his County debut and a first Championship appearance since May 2017, when he lined up for Rotherham against the Rams.

The 37-year-old came to Derby’s rescue with a superb late save from Gillesphey’s free-kick.

“It’s about our squad and the way they prepare,” added Eustace. “Richard has been working his socks off for an opportunity and I was excited to put him in.

“I’m delighted for him. He played a big part in the win today.”

The Rams held out despite Clarke’s dismissal, a second booking for a foul on Kayne Ramsay, five minutes from the end.

Charlton have won just two of their last 13 matches and are hovering perilously close to the relegation dogfight.

“I’m disappointed really, I felt the goals were avoidable,” said boss Nathan Jones. “We’ve struggled to keep clean sheets and defend the way we want to and that’s what has cost us.

“Second half I thought we were excellent. They had one chance and scored and that’s the disappointing thing.”