Couple of things. First, not really anywhere for Gary to go BUT up; he only played about 23% of the defensive snaps last year and he wasn't very exceptional on those snaps. He rushed the QB 152 times last year and got pressure 15 times, that's a 9.86% pass rush productivity; this is a nice way to normalize players based on productivity per snap when players have vastly different snap numbers and pressures includes sacks, hits, and hurries. For comparison, Preston produced 55 pressures on 456 rushes (12.06%) while Z produced a whopping 104 pressures on 594 rushes (17.51%!). I don't have access to anything but entire season pass rush stats so these percentages might not be exact, but they are consistent among the three and you can see that Gary wasn't really close to being as good a pass rusher as either of the Smiths.
Other pass rush productivity percents: TJ Watt (15.8%), Calais Campbell (13.79%), Joey Bosa (14.49%), Kyle Van Noy (12.93%), Markus Golden (9.60%)
As you can see, Z is an elite pass rusher while Preston is above-average and Gary was almost average (Golden's rate was 43rd in the NFL among edge defenders). Now, Gary was a rookie so I hope there's improvement but there is legitimate concern considering the questions about him coming out of college.
He was about as good as either Smith at stopping the run, but that skill is something you want out of a guy after the third round, not the top-15; if Gary turns into the best run stopping edge defender in the NFL, he will have been a bust if he can't also rush the QB at an above-average level.
It would seem that Gary will most likely just be backup for the Smiths again this year in case of injury (unless one of the Smiths falls off a cliff) but, if all are healthy, Gary seeing more playing time would mean that one of the three is going to be playing DT/DE (possible on 3rd downs with Z).
