The way I understand it, whenever you load a game (no matter when you saved it), it makes it so players ask for ridiculous salaries, and it stays this way until the following Tuesday, at which point everything goes back to normal. So saving on a Friday doesn't mean the salary bug won't occur. It just means it won't really affect you unless you really wanted to sign a free agent between then and Tuesday. The reason for doing it on a Friday is that the week's events have already occurred. If someone got hurt in practice you already had the opportunity to sign someone else. And if a player on your team wanted to negotiate an extension, he already asked you about it (they don't ask you on the weekends). So don't be alarmed when you load your game and look at the free agents and they want ridiculous money. That is always going to happen. It'll all go back to normal once you get to Tuesday.
To sum all that up, saving on a Friday doesn't prevent the salary bug. It just minimizes the effects of it. Just don't sign anybody between the time you load and Tuesday, and you'll be fine.
(And if I got any of that wrong, someone please correct me.)