I think our defense may surprise you a bit. Porter was struggling with injuries and being played out of position as a 43 LB last season, but towards the end of the year when he settled and got healthy, he played well (one of the few ... if anyone was even watching by that point in the season lol). Porter should be productive for us this year now that we're running a true 34 and he's back in his natural position.
We didn't trade Jason Taylor, and he's still got enough gas in the tank to make plays. He may even have something to prove when everyone he faces makes Dancing With The Stars trash talk comments at him.
While everyone is sad to see Zach go, it was for the best. Remember, traditionally when we have had Zach healthy we've been a good defense, and when he's been out of the lineup we've been poor. Last year he was out of the lineup almost the entire season, and we were very poor. We brought in 2 new ILB starters in Ayodele and Torbor/Anderson. While none of those players is Zach, the new scheme and 2 new talented players should improve our LB corps and free up Porter particularly to make more plays.
Our DL really suffered last year, and that was our Achilles Heel (along with missing Zach of course). Letting Carter go proved problematic, and Roth wasn't healthy nor was he ready for prime time. Traylor was still good but even less able to play more than 1 or 2 plays at a time. Our backups (Soliai, Fifita, etc.) just weren't up to par. Bringing in Jason Ferguson is a huge upgrade there as he plays more plays than Traylor and is a bona fide very good NT. Plus hopefully Soliai and whomever else gets minutes there will be more experienced. It's a new scheme, so this is the crucial area to watch.
Holiday isn't a great fit in the 34, and he was one of our more productive players, so that's going to be a rough transition. Roth simply cannot play 34 DE, and I see him being let go or traded. Starks should do an admirable job at LDE. Holiday and Merling will likely rotate at RDE, although both are a little light for the position at the moment. Langford will likely backup everywhere and rotate in at LDE spelling Starks. Rod Wright should really come to the forefront in this system, as he can play all 3 positions up front. Ultimately, I think we overdrafted 34 DL guys because we really lack the personnel to play it at the moment. None of the holdover starters is a good fit for a 34 DL. That leaves us with Ferguson (trade), Starks (big contract FA who will start at DE), Merling (high draft pick), Langford (drafted higher than expected), Rod Right (veteran developmental guy with some talent but not enough to start, but has the size/skills needed to play in a 34 DL), and Paul Soliai (enigma with strength, etc., but the light hasn't gone on for him yet). That's not the most impressive list. If we fail defensively, that's going to be one of the main reasons.
Our secondary is truly horrific. Will Allen is a good corner--when he is healthy (both games!). He's not big enough, but given what we have that's the least of our concerns because he has some legit talent. He is injury prone, and that's going to be our undoing. Ditto for Andre Goodman, who hasn't seen a training table that didn't make him go "oooooooooh comfy!" In this league you need 4 CB's these days ... our barrel ends at 2 deep. Lehan was resigned ... but he sucks IMHO. Please don't even go over the other 'options' at CB behind Lehan, they're various flavors of terrible.
Safety was shored up a bit. Bell has talent when healthy (both games too!), but he's going to get injured as usual. Luckily for us we brought in Crocker who is an average safety, making him a huge upgrade over what we had last year. Sad but true. Jason Allen really came on last season and had a good year, hopefully that continues. All in all, CB's are a much bigger need than S's as nickle packages play about half the time and dime packages play a lot too. I'm most frustrated that we didn't add a CB in a draft deep in CB talent.
Will we be great? Most definitely not. Will we be the worst in the league? I don't think so. I think somewhere in the middle 1/3 of defenses is attainable for us this year, but likely to be in the bottom half somewhere. Next year we'll need to really remake the defense with several DB's, at least 1 pass rusher OLB and probably 1 ILB, and at least 1 more DL.