Derby County manager Frank Lampard called his side's FA Cup win at Southampton "magical" after the Championship side came from 2-0 down to win on penalties.
Derby had a goal ruled out in the first half by VAR but rallied with two goals in six minutes to set up a fourth-round trip to Accrington.
"It takes a lot to come back against Premier League opposition and show that fight," Lampard said.
"They made me proud."
Craig Bryson thought he had put the Rams ahead in the first half but had his goal overturned for offside - a decision which former England captain Alan Shearer, speaking on Match of the Day, felt left them "very hard done by".
Southampton then went into a 2-0 lead thanks to two goals in two minutes from Stuart Armstrong and Nathan Redmond but - as they did in the first game 11 days ago - the underdogs fought back thanks to goals from Harry Wilson and Martyn Waghorn.
Saints sub Redmond then missed his penalty in the shootout to allow Derby skipper Richard Keogh to convert the winner in front of more than 1,000 travelling fans.
"At 2-0 down it was easy to give up and they didn't," Lampard, who won four FA Cup finals with Chelsea, told BBC One. "I've got a really good dressing room with great characters. They wanted to play, to run when fatigue kicks in and we thoroughly deserved to win the game.
"I'm delighted for Richard Keogh. Everyone at this club knows how important he is, the club means so much to him. He asked to take one. I know he's got quality, he is a man of strength, the sort of man you want to take that.
"A big thank you to the fans because it's half past 10 when the game finished. They're going to get back to Derby at whatever time and they're probably working on Thursday too so a big thanks to them because they helped us get over the line."
Southampton manager Ralph Hasenhuttl said that his side did not deserve to progress and felt that the Rams' previous comeback affected his players, and the crowd.
He told BBC Sport: "Congratulations to Derby County. When they fight like they did in the two games, they deserve to go through to the next round.
"They got a goal from a set-piece and you could feel everybody thinking about the first game and getting a bit nervous."
-- Courtesy of BBC Sport