It was Chopra's fifth goal of the campaign and McCarthy saluted the striker and said there was never any chance of him leaving on loan, despite approaches from rival clubs.
"Some clubs asked about him but I made the decision that we needed him and needed his goals," McCarthy said.
"His winner was the one bit of real quality in the whole game. From the time he made his run to the time he got across the defender and held him off to the minute he finished with his weaker left foot.
"The defender was all over him and the keeper narrowed his angle, so it was real quality. He showed a bit of class.
"He's got something about him. He scores his goals but it was the way he went about his job and worked hard.
"He stopped them playing from the back, as best he could. I thought he was excellent."