Jennings joined the Vikings from the Packers in March and has since had plenty to say about his former employers.
Not all of his comments have been positive, but the 29-year-old did reserve special praise for McCarthy's fresh approach to training.
"McCarthy, he really is mindful of - and this isn't saying [Vikings] Coach [Leslie] Frazier isn't - but McCarthy is one of those guys that he really looks at his team and he evaluates, 'OK, what do we need to cut back today, what do we need to implement today because I want a fresh team. I want to get quality work versus quantity.' And that's the biggest difference being a veteran guy and seeing what we are doing," Jennings told KFAN.
"We are pushing through everything, working hard every single day, which is always great to work out, but at the same time, you've got to give and take a little bit."
Jennings has recently claimed that the Packers "brainwash" their players into believing that they are the best.