There's a 10% "tax" when you pick up someone off the waiver wire, so net of everything else you could drop just the one player and pick up a replacement with a salary of around $3.6 million who is available on the waiver wire under the GM's Office tab.
However, you also have some other options and some "free" money to play with in an open league:
* You have 6 AAA hitters and 2 AAA pitchers who you could use to potentially fill some of the holes. They can fill PA/IP to help you out, and there are usually a couple decent options in AAA. While these players all are listed with a $200,000 salary, in an open league they're actually much better than that (see
https://www.whatifsports.com/forums/Posts.aspx?TopicID=388184 for more information on what the grades translate to in terms of performance and how to identify who your AAA player actually is).
* In addition to the salary of the waived player, you also have $1.6 million (the value of the AAA players) plus however much money you didn't use in drafting your team. So if you only spent $79.6 million in an $80 million league. You'd have the salary of the waived player plus $2 million ($1.6M for the AAA players, $400K in unused salary) to play with..
Don't abuse the waiver wire - the 10% penalty adds up quickly - but in a situation like this where you drafted sub-optimally it can definitely help.