Tizzard has chosen to go with a fresh pair of hands on the 11-year-old after he fell for the second time in his last three races in the Charlie Hall Chase at Wetherby on Saturday.
The 19-year-old, who rides principally for Tizzard and Paul Nicholls, schooled Cue Card on Wednesday morning.
He said: "I schooled him this morning and he felt A1. I'm very much looking forward to riding him. It is a great opportunity for a young jockey to pick up a ride like that and the target is the Betfair Chase.
"I ride out for Colin every Wednesday and I know all the horses well. I've not really got any commitments in Graded races so it will be nice riding a horse like that as these opportunities don't come around too often."
Cue Card's next race is due to be the Betfair Chase at Haydock on November 25, a race he has won three times in the past, twice with Brennan on board.
Tizzard said the decision was nothing personal but that he felt he owed it to the horse to try something different.
"I spoke to Paddy on Monday and said I thought the horse deserved to have a change of rider as he has fallen twice out of the last three times. He said it was fair enough," said Tizzard.
"It's not a big issue changing jockey as we do it all the time, but it might be on Cue Card because of his profile. It is a different set of hands on board so we will see what happens."
The trainer added: "Harry might be available for two or three races, whereas a lot of the top jockeys are already on the best horses.
"I like the idea of having a younger man on him. I've known Harry all my life and he has got plenty of experience. He has ridden a lot of winners for us and he is a good young rider.
"I consulted Jean (Bishop, Cue Card's owner) about it and she is a very loyal person, but she thought the horse deserved a new rider.
"He (Cobden) will be scrutinised, no doubt, but getting on Cue Card when you are 19 years old, he should be chuffed."
Cue Card is 5/1 with Sky Bet for the Betfair Chase.
