The Royals, who lost 3-0 at home to West Ham earlier in the season, were handicapped by Brynjar Gunnarsson's red card on the half-hour.
"We were very conscious of the first game this year when it could easily have been 6-0," said Coppell. "For a home team, that hurt us and today was an opportunity to try and salvage something from that game.
"We started brightly and then the sending-off knocked the chair from underneath us a bit, but we were solid, we were together and the players rose to the challenge.
"It was a controlled performance. The problem when you only have 10 men is when you attack and lose your shape.
"To keep your shape together all the time you have to work hard - but it is not a marathon test by any means.
"We have a training ground routine where we play eight against any number and if you are communicating well enough you can withstand it most of the time."
Gunnarsson was sent off for a two-footed lunge on Hayden Mullins, and Coppell could not complain about the dismissal.
He added: "I, like everybody else, wants to see the two-footed jump tackle removed from the game.
"I know Bryn didn't mean anything by it, but by the strict letter of the law it was a two-footed jump tackle and he had to go."