These two stats will often be an inverse of each other for good offenses simply because good offenses get more big plays thus limiting the number of plays ran. The top two offenses in yards per play (and high in most offensive respects) are Oklahoma and Central Florida and they have play per game numbers similar to Nebraska. Stanford is 4th in ypp and rank near the bottom in plays run. Ohio St is an example of a team that ranks high in both due to consistency in medium yardage plays, like we saw against them.
in general, plays ran has become an inflated statistic because teams are using high play totals to exploit substitution patterns and not so much because there is an intrinsic benefit to running more plays. It's a drive based game, not play based, and so the ultimate measure is drive success. Running more plays may or may not equate to more drives, depending on teams and conditions.
What Nebraska needs to focus on is better sustaining drives and lessening the strain to sustain drives by getting bigger plays, and that deficit as noted here and discussed last week is in the running game. The speed and acceleration of the current backs leaves a lot to be desired, IMO.