Why hasn't 3rd round QB Jacoby Brissett signed with the Patriots?

The New England Patriots have agreed to contracts with every single rookie, other than 3rd round quarterback Jacoby Brissett. Brissett has decided to not use an agent for his rookie deal, but that can't be the only reason why a deal hasn't been finalized.

90th overall RB C.J. Prosise has signed a contract with the Seahawks, while 92nd overall CB Brandon Williams has signed with the Cardinals; Brissett was selected 91st overall. Couldn't he just take the average of the two sandwich deals?

ESPN's Mike Reiss pointed out a hitch when it comes to third round picks in his Sunday Notes.

"While nearly 75 percent of this year's draft class is already under contract...the third round has only produced 15 signings among 35 picks. Why so many third-rounders who have yet to sign? One NFL salary cap man relayed that third-round negotiations have proven to be more challenging than other rounds in recent years.

"The reason is that first- and second-round picks can receive a maximum of 25 percent allocation of a team's rookie salary cap, but because the third round doesn't max out at 25 percent, there is often debate over what the correct percentage should be. That has created a situation where the third round has been the spot in the draft where some agents are pushing for more annually, such as the inclusion of workout bonuses in the deals."

And this extra money is extremely important when it comes to quarterbacks. PatsCap's Miguel pointed out on Twitter that quarterbacks selected in the third round typically receive "a premium" and earn more than other players in surrounding draft slots.

In 2012, 3rd round quarterbacks Russell Wilson and Nick Foles saw additional money. In 2013, 3rd round quarterback Mike Glennon and 1st pick of the 4th round Matt Barkley saw additional cash.

In 2015, 3rd round quarterbacks Garrett Grayson and Sean Mannion did as well; Quarterback Bryce Petty, the 4th pick of the 4th round, did not.

This year, Brissett and fellow 3rd round pick Cody Kessler remain unsigned, while the Raiders' Connor Cook, taken 2nd in the 4th round, signed a contract without a premium.

This premium is likely the big hurdle between the Patriots and Brissett.

Wilson, taken 75th overall in 2012, received a contract valued between the 67th and 68th overall picks, for roughly an additional $190,000. Foles, taken 88th overall, signed a deal between the 78th and 79th overall, for roughly an additional $80,000.

Glennon, taken 73rd overall in 2013, saw roughly $204,000 extra; Barkley, taken 98th overall, received roughly $63,000 more than his draft slot. Grayson, taken 75th overall in 2015, saw roughly $258,000 extra; Mannion, taken 89th overall, saw an absurd roughly $289,000 extra.

We expect the dollar amount of the premium to increase over time, as salaries increase, but the premium should remain a certain percentage of the projected salary.

Using these points, we can create a graph of an expected premium based upon draft position:

Based off this partially formed graph, we can project Brissett to receive a 4.2% premium over the $3.02 million contract he is projected to receive.

Of course, this 4.2% is heavily influenced by the huge deal that Mannion signed. The 3rd round QB premium graph makes a lot more sense when Mannion is removed:

Based on this chart, Brissett would receive a 2.9% premium, which results in a difference of roughly $38,000 compared to the first chart.

While it would be nice to have more data, this is what we have to work with- and the lack of history explains why Brissett and the Patriots are still negotiating to close the $38,000 gap between the two sides. Brissett will likely be arguing for the 4.2% premium, while the Patriots likely want to undercut the 2.9%.

It would help if fellow 3rd round quarterback Kessler came to terms with his own contract, but he is likely waiting for Brissett to set the market for late-3rd round quarterbacks.

Until the Patriots and the rookie can figure out a reasonable premium, Brissett will remain unsigned.