Hasselbaink says he had no say and wasn't pleased.
"I was absolutely gutted," Hasselbaink told BBC Sport. "More gutted because Mourinho never spoke to me."
He believes there was outside influence on Mourinho's decision.
"I bet you that Mourinho had been told that I was a difficult lad," Hasselbaink says, "hard to work with and all that kind of stuff - which was not the case at all."
Meanwhile, Hasselbaink continued to be a high scorer for Middlesbrough over the next two seasons.
He believes, though, that he was robbed of an opportunity to get silverware with Chelsea.
"They got Drogba - what a signing - but surely I could have featured alongside him. I've spoken to Mourinho, he said, 'yes, I made a mistake there.' I don't care what he said. He should have kept me and I would have had a medal."
Asked whether he believes that current Roma coach Mourinho is 'the special one', as the man himself famously claimed on arrival in West London, Hasselbaink disagrees.
"He's a brilliant coach, absolutely magnificent what he's done in football, but he was never the special one for me."