It was still goalless when Giorgio Chiellini appeared to mis-time his tackle on Sergio Floccari during a scoring opportunity.
Instead the referee waved play on and the Biancocelesti fell to a Simone Pepe goal after Cristian Ledesma's dismissal.
"I don't know what to say, but unfortunately it's not the first time this has happened to us," said a visibly irritated Reja.
"Apparently recriminating gets you nowhere. It was a clear penalty on Floccari and I don't know what it could've done for the game, but seeing incidents in other matches there were spot-kicks awarded for a lot less.
"I'm not saying it because it is my player. I am just being honest, you can see the footage quite clearly."