The New England Patriots have signed Buffalo Bills restricted free agent RB Mike Gillislee to an offer sheet for $6.4 million, with $4 million in cash for the 2017 season. If the Bills do not match the Patriots offer, then New England will also have to send a fifth round pick to Buffalo.

So why is Gillislee worth $6.4 million and a fifth round pick?

Let’s split this up into two parts.

Is Gillislee worth $6.4 million over two years?

Gillislee will average $3.2 million per season, which ranks 20th in the league out of veteran running backs (coincidentally, Patriots RB Rex Burkhead was 20th until this Gillislee offer). While these numbers sound large for the Patriots, it’s actually a very fair price point on the open market.

There are very few starting-caliber running backs on non-restricted veteran contracts that make less $3 million per season. Danny Woodhead and Dion Lewis are pretty much the only exceptions to the rule and neither can remain healthy enough to warrant more money.

Teams fill up their running back depth chart with players on rookie deals, but we’ve reached a point where the position is so undervalued that the third or fourth string linebackers (Shea McClellin, $3.02 million per year) and defensive tackles (Lawrence Guy, $3.35 million per year) are making more than the top running backs.

The concern with Gillislee should be less about “is $3 million too much to pay for a running back” and more “can Gillislee be one of the top running backs in the league?”

All the numbers point to a resounding yes.

Football Outsiders rated Gillislee as the #1 running back by DVOA at +45.0% and #1 in success rate at 66%. He’s was incredibly efficient in 2016. He also posted a +20.9% DVOA in 2015 on 47 attempts.

Over the past two seasons, Gillislee has carried the ball 148 times for 844 yards and 11 touchdowns. That represents 5.70 yards per carry and that’s exceptional production over a non-fluky number of carries.

If Gillislee can match his efficiency over the previous two years, then he would represent a major upgrade over LeGarrette Blount. Blount earned $1.75 million in 2016 and wanted more money in 2017. Gillislee’s improvement over Blount is worth the price.

Is Gillislee worth an additional fifth round pick?

First, can you name the Patriots past three fifth round picks? Stumped? Well, it’s a difficult question because the Patriots have traded away their original fifth round pick for six-straight seasons. LS Mean Joe Cardona was the team’s fifth round pick in 2015. The previous fifth round picks were OT Marcus Cannon and TE Lee Smith back in 2011.

Why do the Patriots trade away their fifth round picks? Well, it’s because teams value fifth round picks far greater than proven NFL talent, for some weird reason.

The fifth round is when the NFL Draft stops being a science and starts becoming a lottery, where players fail to make a roster or contribute on a regular basis.

The Patriots have given up their fifth round selections in pick swaps for a player and a later pick, and have acquired veterans like DT Albert Haynesworth, WR Chad Johnson, DT Isaac Sopoaga, LB Jonathan Casillas, WR Keshawn Martin, and LB Barkevious Mingo.

Some acquisitions work out better than others, but the Patriots will always trade their lottery ticket for a player with proven NFL experience. The odds of success for a fifth round player is not much greater than those in the sixth or seventh rounds, which is why the Patriots are happy to accept a pick swap; they keep both their lottery ticket and get a player.

But giving up a fifth round pick for Gillislee is different because New England will not be receiving a draft pick in return. Gillislee will be the Patriots fifth round draft pick in 2017.

The average running back selected in the fifth round gains less than 500 yards from scrimmage over their first two seasons in the league. If Gillislee can crack 500 yards over two years in New England (and he should, if he’s healthy and replacing Blount), then he will have exceeded the production of a running back taken in the fifth round.

And when evaluating Gillislee, we have to look at the full picture: he will not be playing under a rookie contract, so his production will have to exceed his draft slot by enough to warrant the additional money. How many extra yards will Gillisee need to produce?

One study suggests 200-700 more yards per season, so we can argue that Gillislee needs to produce 950 yards from scrimmage in 2017 in order to validate the acquisition. After watching LeGarrette Blount gain 1,199 yards in 2016 behind a young and improving offensive line, it wouldn’t be a surprise to see Gillisee far surpass his necessary projection.