The 31-year-old striker joined Melbourne City on loan last month after struggling to justify his £12 million transfer fee to Aston Villa.
The former Leeds United and Fulham marksman cost the Villans a pretty penny in the summer of 2016 but McCormack managed only three goals in 22 games.
He joined Nottingham Forest on loan in January after Bruce accused him of missing training, though he scored only once in seven Championship games for the Reds.
And the Aston Villa boss has told The Express and Star that he has some regrets over not being able to help McCormack get over his slump, revealing that he and the player had hoped to turn things around this past summer.
He said: "There are one or two things I would have changed. I was disappointed, for example, with how Ross McCormack transpired.
"Even in the summer, I shook hands with him and said 'let's make a fist of this if we can'. Unfortunately it didn't happen so there's one."
McCormack was signed by Bruce's predecessor Roberto Di Matteo, but he didn't look any better under the Italian than he did under the former Sunderland boss.