Justin Tuck can’t tell you what’s wrong with the least productive pass rush in the NFL and he can’t tell you how to fix it. But the Giants’ veteran defensive end can tell you this: It’s not completely his fault. Heck it’s not all the defensive line’s fault either. “If I was the only one having a bad year numbers wise then you could easily say ‘Justin doesn’t have it anymore’ ” Tuck said Thursday. “But when Kiwi (Mathias Kiwanuka) is not having a good year when JPP is not having a good year when Cullen (Jenkins) is not having a good year when whoever else is not having a good year you might want to look into it a little deeper than the numbers.” So who is to blame for the mysterious decline of this once-great pass rush? The Giants will enter Monday night’s game against the Vikings still searching for that answer. For years they relied on a ferocious pass rush but that’s been conspicuously absent during this 0-6 nightmare of a season. This is a team that won the Super Bowl two years ago behind a defensive line that collected 48 sacks and covered up issues throughout the rest of the ‘D.’ But this season? The Giants have an NFL-worst five sacks in six games. To Tuck that’s at least partly because his unit has been stripped of opportunities to succeed. He said that “it starts with what I do individually and I think everyone on that D-line feels the same way” but he also indicated that his group was being crippled by opposing game plans maybe some of the Giants’ own offensive woes too. In the glory days he recalled Giants defenders chased down quarterbacks when Big Blue had a lead essentially closing out games after dominant offensive performances. But these Giants have led for just 2:42 in the second half so there have been few chances to tee off.