In a typical 4-3 front, there is a 1 technique DT (aka NT/overtackle) who lines up in one of the A gaps between Center and Guard. And then a 3 technique DT (aka undertackle) who lines up in the B gap between Guard and Tackle. The DEs play 5 technique outside the tackle.
So by putting both DTs in the A gaps, that is a little different. Though I'm not sure exactly how it changes things for the o-line and their blocking assignments, it apparently worked for us. I think to some extent it clogs and collapses the middle of the line and forces runs to the outside, where a speedy LB like Leonard can make plays.

It is unusual, because it essentially means both DTs were playing 1 technique, which is an unusual way for a defense to line up, but also achieved the goal the defense had to prevent inside runs and force them more to the outside, where the speed of the LBs and secondary could help more. The usual way a 4-3 DL lines up is with a 1 technique NT in the A gap, a 3 technique UT in the B gap between one of the OGs and OTs, a 5-7 technique DE lining up either square with the tackle or to his outside shoulder in the C gap on the NT side and a 7-9 technique lining up anywhere from the C gap (between the OT and TE if there is a TE) to the D gap (to the outside shoulder of the TE if there is a TE) on the UT side. This alignment can be altered by back 7 personnel and their positioning, which can alter the positioning of the DEs (i.e. a LB near the line might turn a 7 technique into a 5 technique) and which side of the line the NT and UT are on typically. Both DTs playing one technique takes away the A gaps, but forces the DEs or LBs to cover the B and C gaps. That was the point, they were trying to force the Titans into outside runs if they were going to run with Henry.

It makes traps and other inside zone runs more difficult to execute, because there's no 3 technique to trap, which is what the announcers commented on in the broadcast.

I don't think it's totally unheard-of. The two Williams DTs that played for the Vikings would line up that way at times if I remember right.

Well, you have the D and the A in your name, but you are missing the M.

We do all different kids of things with dline alignments. We overload one side of the center at times, double a gap the d’s Like was mentioned, bring backers at the a gap and widen 3 tech the dts. We drop the nt a few times a game it seems.

I encourage everyone to quickly scan the lineup before snap.