Starting any sane discussion of a player's worth as it relates to an NFL team's needs and cap has to begin with an understanding of NFL player contracts. To that end, let's please look at the $20 mil/ 4 year deal recently signed by Leodis McKelvin of the Buffalo Bills. Understanding this is important because, depending on how much money per year Mr. McKelvin makes relative to the salary cap, it will determine how smart the deal was.
Let's assume that $5 mil/ year is too high for a cornerback of Mr. McKelvin's limited ability. There have (to my knowledge) been no reports stating how the contract plays out in actual and cap-related dollars over the course of the four years. Regardess, it's a lot easier to make an argument against the contract if he is actually making $5 million per year than if it were less money than that.
But what if, as is the case with most NFL contracts, the Bills don't actually plan on paying McKelvin the entirety of his contract? There is a reported $7.5 mil in guaranteed money here, so they definitely plan on paying him that much.
Here is a possible way for his contract to be laid out:
$4 mil signing bonus
Year 1 - $2.5 mil
Year 2 - $3 mil
Year 3 - $3 mil
Year 4 - $3.5 mil
Roster bonuses of $2 mil each of year 3 and year 4.
The Signing bonus is prorated against the cap at $1 mil/year. So, Mr. McKelvin's cap numbers in this scenario would be $3.5mil /4 mil /6mil /6 mil. He would, theoretically in this scenario, make his guaranteed $7.5 mil in the first two years. After that, the Bills can cut him and he will count only $2 mil against the cap, for the remainder of the prorated signing bonus.
Thus, if the look at Mr. McKelvin deal as a two-year deal for $3.5 and $4 million, even for a low-grade starting CB, that's certainly not terrible. It is a lot easier to make an argument that Mr. McKelvin is worth being kept by the Bills at that pay rate than at $5 million per year.
One way or another, if you are going to argue about how much Mr. McKelvin is worth, please come to the argument knowing the actual amount the Bills plan on paying him relative to the cap. No other numbers matter, unless we're talking about the crazy amounts of money athletes make in pro sports in general. And that's a topic for another day.