Di Matteo refused to give Petrov a contract once he recovered from acute leukaemia in 2016.
Agbonlahor told ThreesixtyTV: "I'll hate him for the rest of my life for that. Any other manager with a single bit of heart would have given him a pay-as-you-play [contract].
"There's a month, or there's six months, let's see how you are. To be so ruthless and heartless to not even give him a chance, you know what I mean?
"Imagine you come back from that horrific disease, you've got yourself fit, you've lost all this weight that you've put on through your treatment.
"You've come back, you've done every run that the 19-year-olds have done in pre-season and you can't give me anything? Do you know what I mean?"