A rhombus is defined as a closed geometric shape with four equal sides... Like a baseball diamond.
Today, let's think about three words from that definition: closed, four, and equal. This should be your plan for acquiring relief pitchers in fantasy baseball. Build a rhombus.
First of all, it is important to deal with some of the prevailing wisdom out there regarding closers and why people say what they do. Matthew Berry at ESPN is quite famous for saying, "Never pay for saves." I've heard on other podcasts (the MLB.com one, iirc) that you should always invest in high quality closers because it is an easy way to gain a discernible advantage in your league.
There are those kernels of truth once again, my friends. Let's work through them.
First of all, why does Berry say, "never pay for saves"? Denominators. Often times people will look at closers as being four-category players since they get strikeouts and usually have low ERA's and WHIP's. The problem with that is that they pitch so few innings (the denominator) that they won't make a dent in those three categories, and that is why Berry says what he does. He views closers as one-category players and they mostly are. Mostly. There's your kernel of truth.
The other part of his view is that you can always get saves off of the waiver wire... Saves come into the league since it is such a volatile role in real life baseball. This is true, but do you really want to rely on your ability to get some saves from a competitive source? ...eventually?
What I want you to do is to consider the rhombus. Go out and get four closers that are of roughly equal value, but don't spend too much on any of them. This will give you a gigantic advantage in saves and a little extra contribution in K's, ERA, and WHIP. You just stick them in your lineup and leave them there. In a 10 or 12 team league having four good closers virtually assures first or second place in saves, and while the denominator of innings pitched won't move the needle too much on those other three categories it also won't hurt you any. And, hey, those extra contributions might push you up one or two spots in a couple of those categories. It could literally bump your season-ending point total up by maybe 3 or 4 points. At the very least it won't hurt you, which is awesome. This is a market inefficiency that you can exploit.
More good news: If you have four closers and one gets injured you won't be scrambling for a replacement. If one is a bust, same thing. If you build a massive lead in saves you can trade one. If you are lucky enough to pick up some saves off of the waiver wire, more trade fodder. It's all good.
Also, I should note that this is really for mixed leagues. If you are drafting in AL-only or NL-only you will only need 3 closers at the most, or even just 2 if it is a league of 12 or more teams. A 10-team single league is a grey area... See if you can get 3, but this strategy is probably still very effective with 2.
Now, how do you pick four equal guys that don't cost too much? Easy enough... Start by making a list of one closer (or most likely candidate) from every team. Then, throw out the top of the list and the bottom of the list. It should be obvious to you who the really elite and expensive guys are and who the crappy options are who might not even have the job for sure. As a rule of thumb I would take 10 from the top and another 10 from the bottom. So, you'll be wanting to get four of those guys in about the #11-#20 range.
In an auction draft you should have a good idea of about what they will cost... set a budget and go for it.
In a snake draft wait until 10 closers go off the board and then start making your picks. At that point you are probably going to go with 4 closers in about the next 8 rounds or so. It will probably be something like rounds 9 through 17.
So, for example... if you grab closers in rounds 10, 11, 14, and 16 you should be in good shape. This is a significant investment, but most of your starting lineup has already been taken care of early. Think of it as spending several middle-to-late picks dominating a category and contributing to three others at the expense of having higher quality bench guys.
That is a worthy swap every time. Think rhombus.