Cruz was targeted 143 times by Eli last year, and Welker was targeted 174 times by Brady. Let's assume Eli had thrown 31 more balls Cruz' way last year, and he had caught all of them (which would be a feat considering he was second in the league in drops last year). By multiplying those 31 catches by his 12.7 YPC you get 393 yards. Add that to his total of 1.092 receiving yards and you'd get 1485 yards, or 120 more than Welker.
But obviously, Cruz wouldn't catch all those 31 targets that separate him and Welker. Being that of those 143 balls thrown his way 86 were actually completed, his catch rate was 60.1%. So of those 31 targets, we could reasonably expect 19 being completed, which would net him about 242 more yards. So, had he been targeted as much as Welker he'd end up with around 1334 yards on 105 catches, which is less production than Welker had.
But even if this exercise shows that Cruz would still have a worst season than Welker had he seen the same amount of footballs thrown his way, your argument leaves out a crucial detail, which is, why do you think it is that Cruz was targeted less than Welker? Isn't it because he was open less often? And explain to me why did he have 32 less catches than Welker, while only been targeted 31 less times. His catch% was SIGNIFICANTLY lower, and his drop% was higher too. So either he wasn't open enough to get more targets or Eli didn't trust him enough to come up with the football to target him more. That's the reality of the 2012 season. Your scenario of "oh, if he received the same targets he would've been more productive" is both false, as demonstrated above, and also menaningless, because being targeted less frequently than a guy who plays the same spot as he does is, in itself, and indication that he doesn't stack up to Welker as a slot receiver.
