But the Pompey boss has praise for his players for their performance, as they rescued a point late on to extend their unbeaten league run to 18 games.
Mousinho has words of criticism for referee Rebecca Welch and her display at Pride Park, after she gave a penalty against Regan Poole handball near the end of normal time.
Colby Bishop cancelled out James Collins’ spot-kick five minutes into stoppage time to give Pompey a richly deserved draw against Paul Warne’s side.
Mousinho celebrated the late goal, but in reflection felt his side maybe deserved a greater reward.
He said: ‘I was furious when the penalty was given. I thought it was the accumulation of a number of bizarre decisions through the afternoon.
‘Can I understand why the penalty was given? Maybe, but it comes off Regan’s knee and unless he cuts his arms off I’m not sure what he’s supposed to do there. He’s trying to defend.
‘To get back into the game after that penalty, I was thrilled.
‘The boys could have used every excuse in the book, saying we were unlucky having played so well not to come away from Pride Park with anything.
‘The feeling when we scored was elation, but having settled down we maybe slightly rue the fact we didn’t come away with three points.’
In a stiff test of their credentials, Pompey looked the better side for long periods and played some decent football against the fancied Rams.
Mousinho felt he could see the marked progress from his team after the same result when the teams met at Pride Park in April.
He said: ‘If you contrast the two performances here. We played okay last time but were hanging on.
‘Here, I felt we were the better side without being good enough at certain things we did.
‘We were a bit sloppy in terms of our possession at times, but created the better chances.
‘In the second half I didn’t have too much criticism of the lads whatsoever - I thought we were really good.
‘We created chances, good on the break and brave on the ball.
‘The only thing we didn’t do was put the ball in the back of the net.
‘We didn’t have a shed load of chances, but created enough to go ahead.
‘So I’m really pleased with what I saw and we fully deserved a point.'