First of all, I think the Darby signing is a great move. A veteran leader who will help the younger guys on the roster, and whom they will pick-up in the draft, develop. They have brought in smith to serve the same purpose for the Lions' young secondary. Bullocks and Alexander are progressing well, but Smith will be a solid backup and provide mentoring for them.
I keep hearing people go "Spikes" - why??? He has been injured, ineffective, and doesn't play MLB. Lewis and Lenon are solid at SLB IF - big IF - there is a solid MLB. Simms has the weak side locked up. I Laughed out loud when I saw someone question how to replace Bailey...considering he ended the season as a backup, and UDFA who can actually tackle someone will do.
With all the high-picks lost in FA the Lions may even be looking at a compensatory pick this year. That would give Millen the Ammo he needs to turn one or both 3rds into 2nds again. Considering there is a lot of quality talent at the Lions' need areas projected to be available in the 2nd this year, it makes a lot of sense. I can see them waiting into the 4th for a DT now though, depending on where/how they trade and who is available.
Now, I have seen a lot of people questioning why the Lions picked up a guys who doesn't sack people. In the T2, the Dline - especially the DT's, rotate a lot. One Tackle clog up the middle against the run, and takes on the C and one of the two G to keep the middle secure against the run, and trys to get into the backfield and stop the runner. The QB is a nice bonus, but NOT their focus. This is the position that Darby will fill on running downs, with Langston Moore coming in on passing downs.
The other Tackle (Redding) keeps an eye on the run, and tries to take advantage of the double team on the DT, or a G sliding to help the tackle with a DE, to get into the backfield to pressure the QB. With the first tackle collapsing the pocket, the second tackle tries to help collapse, and break through to the QB.
With the DT's pushing up the middle to create pressure, this should force the QB to roll slightly to either side. The DE's should be able to take advantage of single coverage to get pressure on the QB and force him back into the pocket -- which also prevents many of the roll-out screens that killed the Lions last year.
Where the Lions broke down as the season reached the second half last year was in a couple of areas on the Dline. Rogers was still taking two blockers, but he wasn't creating any pressure. Teams then started to keep a TE back to help block Redding and White with a TE, G, and T. This further broke down since Kalimba on the left couldn't beat single coverage - EVER (It seemed anyways). Since they didn't need a second TE to keep Kalimba out of the backfield, they essentially could have 2 backs, 2 Wr or 3 Wr and a single back and still have options open no matter what over the middle. the lack of a true MLB enhanced the problem as Lenon couldn't contain in the middle. This forced Simms to start edging out of his gaps and over toward the middle to help Lenon, and left the weak side open.
When the Dline was getting pressure early in the season, the secondary was able to take advantage of the hurried throws, and the errant passes coming out when the opposing QB was hit as throwing. They also were able to get into the backfield and disrupt hand-offs, and hit RB's scrambling to save a play, and caused quite a few fumbles. the T2 needs corners who can cover okay, take advantage of the pressure created by the Line, and move up and hit like a freight train to stop the run. It basically uses 4 Safeties with above average cover skills. "Shutdown Corners" (that I don't think exist except in Madden-land due to the rules changes) like Bly do not do well. They are good at running with the WR speedily all the way down the field, and jumping in to try to disrupt the pass, or guess on the route and undercut it with speed to get the int. Not the skill set needed in the T2.
The Lions are fairly well set for right now in the secondary, and CB is not the top need -- I have needs in order as follows:
1. OT -- Scott and Backus have both been hurt; they need a 3rd starting caliber OT
2. MLB -- they don't have one, and there are no good veterans available
3. DT -- Darby will be a good mentor and influence, but they need a guy to rotate in & develop
4. DE -- IAF is coming along, but they need a 3rd DE for depth and if IAF is not the answer
5. RB -- Calhoun and KJ are injured every year, and Cason is a special teamer.
6. CB -- You don't need stars in the T2, and what they have will work if the Dline does. This position can be upgraded more next year if needed.
The coaching Staff believes the IAF will be able to bring the pressure that Kalimba could not. Darby will be good in rotation, but I still think they need to draft another DT.
Overall, Marinelli is still trying to clean up Millen's mess. With the salary cap restrictions and the bad drafting and FA signing of the 5 years before he arrived, there was not a lot to work with. That he has the Lions almost back to consistent mediocrity instead of sitting alongside the Raiders with the bottom feeders in just two years says a lot.