Fifita has fewer TDs (7 to 12) and more INTs (6 to 5) than Retzlaff.

He has thrown 7 TDs, but 4 of them have been to the same receiver. Half of the passing yards have gone to that single receiver (he already has 660 yards in 5 games!). He doesn't spread the ball around very much.
(on the flip side, Retzlaff has thrown 12 TDs to 8 different receivers. Lassiter has the most at 3).

Running the ball, Arizona similarly has one primary back.
BYU's diversity here is due to injuries, so I won't make a comparison.

I guess it just seems like this simplifies the defense's job a bit. Fifita can scramble and make plays, but he clearly has targets that he looks for. If Jay Hill can take that target away--and I think he can--then I like our chances at stopping their offense.