A receiver has never won the AP NFL MVP; not Jerry Rice, not Michael Irvin, not Lynn Swann. In fact there have only been three players given the title that weren't either a quarterback or a running back: DT Alan Page in 1971 (MIN), PK Mark Moseley in 1982 (WAS) and LB Lawrence Taylor in 186 (NYG).
There are a variety of reasons as to why receivers do not win the award. Unlike the QB or the running back, there is never a time that they are the only player on the field at their position. A wide receiver may successfully and even impressively complete a play and create offense once they have possession of the ball, but the inherent nature of the receiver position means that they are rarely called upon to bear the brunt of consistent responsibility for creating positive yardage or scoring. Someone has to get them the ball, and that's usually a quarterback who is playing every single offensive snap of the game.
A high-caliber starting running back can become the majority leader of a specific offense or game plan in a way similar to a quarterback. When Adrian Peterson was awarded the MVP in 2012, he carried the ball 348 times; an average of over 21 carries per game. The record for most single-season receptions all-time is 148, set by Marvin Harrison in 2002.
Brinson's argument for Gronkowski is based on Brady's increased effectiveness with Gronk on the field as opposed to without; which is a surprisingly elementary conclusion. Every elite quarterback is better when their best receiver is on the field. The better the receiver, the greater the impact is when they play and the more their absence is felt when they don't. But does it really mean that someone is the most valuable player in the NFL just because the quarterback throwing them the ball is better when they are there?
If Gronkowski were on a team quarterbacked by anyone other than Brady, Peyton Manning, Aaron Rodgers or maybe Drew Brees, there is not a chance in hell he gets MVP consideration. He is absolutely one of the best players receiving the ball in the NFL, and he's certainly on pace to become one of the best ever a his position. So was Jerry Rice and although the GOAT has many awards, the AP NFL MVP is no one of them.
Tony Gonzalez is statistically the greatest tight end of all time (for now); a first ballot HOF-er with a list of impressive records a mile long. He may have made his quarterbacks look better, but his dominance certainly wasn't enough to get any of his teams to a Super Bowl, because a receiver just can't be that x-factor. If they could, you can bet Gonzalez would have player in a Super Bowl. Not only did he not play in a Super Bowl in his seventeen seasons with nary an injury to speak of, but he only played in seven playoff games!
In 2001 when Torry Holt made 81 catches for 1,363 yards receiving and Isaac Bruce made 64 catches for 1,106 yards receiving, it was Kurt Warner who was named MVP. When Marvin Harrison was shattering receiving records and playing alongside Reggie Wayne, it was Peyton Manning who was named MVP. In 2011 when Jordy Nelson and Greg Jennings combined for 2,212 yards and 24 touchdowns, Aaron Rodgers was named MVP. In 2007 when Randy Moss had probably the greatest season by a wide receiver in the history of the NFL with 98 receptions for 1,493 yards and 23 touchdowns, Tom Brady was named MVP.
None of those quarterbacks in any of those examples would have had the type of statistical success they had those years without the talent of those receivers. But Warner was still great after Bruce and Holt, Manning was still great after Harrison, Brady was still great after Moss and Rodgers was still great after Jennings.
When Brady won the MVP in 2010, he was the first quarterback since Brett Favre in 1996 to win it without a 1,000 yard receiver. Last year the Patriots won the AFC East at 12-4, earned a first-round bye and made it to the AFC Championship game; all while Gronk only played in seven games and missed the playoffs. To assert that he is the most valuable player on a team that made it the conference championship without him last year is a gross overstatement.
Gronkowski is a player the likes of which the NFL has really never seen. He is revolutionizing the tight end position. His football intelligence and comprehension of the offense is nearly perfect, he is impossible to defend and his impact is felt even when he is not catching the ball or blocking because he draws so much coverage. He'd be an elite athlete no matter what team he was on, but he is a better football player because he gets to play with Tom Brady. Don't mistake it for the other way around.