Rodgers had a QB rating of 112.2 last season so his rating improved by 22.1 when throwing to Cobb. Eli Manning (92.1) improved by 35.5 points targeting Beckham.
Cobb and Beckham are an interesting comparison. Beckham had a scant 4 additional targets while their catches and TDs are identical. Their average yards per catch is nearly identical...Cobb at 14.1 and Beckham at 14.3. It's not surprising their thrown-to passer ratings would be close, with only INTs not accounted for in these numbers.
Many have cited Beckham having played only 12 games and make the argument he should be regarded at the top of the list for 2014 given he led the league in yards per game played, and his other numbers would go up significantly if projected to 16 games. It does not hurt that the one-handed circus catch, replayed over and over, gets the imagination working overtime.
Lets look at some numbers not included in the passer rating.
As previously noted, Cobb's first downs per target and catch were 56.3% and 78.0%, respectively. Beckham's were 43.2% and 63.3%. That's a meaningful difference.
While Beckham is generally viewed as a perimeter deep threat with Cobb the more humble slot possession type, Cobb had 24 catches of +20 yds., whereas Beckham had only 16 on the same number of catches, with Beckham having 4 additional targets which bears repetition.
Cobb had meaningfully more YAC. But you can't like YAC just for YAC's sake. What is it buying you? I'm saying that with Cobb it is buying more first downs and more long gains.
To the point of Beckham's QB rating spread over his QB's rating being larger than Cobb's, it's probably worth pointing out that the Packers have Nelson and the Giants had Rueben Randall. In other words, one would expect the spread to be larger by virtue of the quality spread between the player in question and his compatriots.
So, what if Beckham had played those other 4 games? To start, it's a conjecture; who knows what that might have yielded. Playing an NFL length season instead of college length season might have had an affect. It's purely guess work. Then there's the counter conjecture...what if instead of throwing the ball 536 times as the Packers did in 2014, they threw the ball 655 times as the Lions have averaged over the last 5 years?
Under that scenario, I would expect Cobb's ridiculous per target numbers to go down (as would Nelson's) given that quantity would likely compromise quality. INTs would go up, one would think, compromising receiver passer rating. But the gross numbers would inflate and the inclination among many would be to rate Cobb (and Nelson) higher than they are even if they are not better players in the bargain.
And that is supposed to make sense.
Cobb's insane production on a per target basis, while also having enough targets to make it meaningful, with impressive gross numbers across the board all on their own, makes for a strong argument for Cobb as the most valuable 2014 receiver.
I submit the problem is that he does not look the part, and he does not make the highlight reels with the occasional one-handed circus catch like Beckham. And slot receivers can't possibly be that good, even if this one happens to be, at least in 2014.