A Shefki Kuqi header gave The Swans a 1-0 win in a fiery encounter at Pride Park which saw both sides reduced to ten men.
Jay McEveley was sent off for the hosts on 65 minutes for two bookable offences and six minutes later Gorka Pintado followed him down the tunnel having received a straight red-card for a reckless challenge on Robbie Savage which led to a mass brawl between players from both sides.
"We played against 14 but we had 12," Sousa said after the match
"Our supporters were outstanding to help us on a difficult pitch, it was difficult to play like I said against 14.
"We showed our spirit more than ever and it is difficult to beat us, we are well organised and I am very happy and proud of our lads.
"I don't want to speak about [Pintado's sending off]. I say we play against 14 and I don't want to explain.
"I have already spoken with the players. We need to control our emotions much better.
"If we control our emotions we don't commit stupid fouls."