"I think Neil was disappointed that I left and that's a testament to how highly he felt I did a job there," said Blackwell on the official Leeds website.
"Whilst he wasn't happy when I left I think he should take a lot of credit in developing someone to move onto bigger things. For me that's a big plus for Neil.
"I can't thank Neil enough and if it wasn't for him I wouldn't be here today. I think he has to take a lot of accolades for seeing someone he developed move on, and I think Neil will be quite proud of that himself.
"He allowed me to develop, he was smart enough to recognise the talent at the time and nurture it. Hopefully my career will go on and Neil Warnock will take a big, big slice of the credit for that.
"I am sure the master will want to teach the apprentice something. I know how passionate Neil is for Sheffield United and he wants to win every game, there is no bigger Blade than Neil Warnock.
"I think it will be a very demanding game physically and mentally, there's no doubt there will be a really passionate crowd and if you don't want to be involved in games like that then you shouldn't be in football.
"I am conscious of how the game went the last time when we went there for the FA Cup quarter-final and many people think it was one of Leeds worst performances, there wasn't a tackle seen in the game. I want us to go there and put in a performance that at least people can be proud of when we come away.
"Leeds were under a lot of pressure because their season was resting on that game and they maybe hyped it up too much and the side did not perform on the day.
"I know Terry (Venables) came under some harsh criticism because Sheffield United did not get the praise they should have for their performance that day, but I do not want to come back from there with criticism ringing in our ears."