The release of Walker based on his apparent regression got me thinking if that's something you would expect out of tackles.

It's obviously tough to measure how well tackles play objectively, but by looking at the ages of the starting tackles in the NFL you can perhaps get a feel for when players start to regress.

So what I did was to take the depth charts at ESPN.com and list each of the starting LTs and RTs and their ages (not sure if this is 100% accurate, but it was the easiest way to put this together quickly).

Here's a list of the tackles and ages, by team:

Team    LT    Age
Ariz    Gandy    30
Atl    Baker    24
Balt    Gaither    23
Buff    D Bell    25
Car    Gross    29
Chic    Pace    33
Cin    Whitworth    27
Cle    Thomas    24
Dal    Adams    34
Den    Clady    23
Det    Backus    31
GB    Clifton    33
Hou    Brown    24
Ind    Johnson    25
Jac    Monroe    22
KC    Albert    24
Mia    Long    24
Min    Mckinnie    29
NE    Light    31
NO    Brown    28
NYG     Diehl    28
NYJ    Ferguson    25
Oak    Henderson    24
Phi    Peters    27
Pit    Starks    27
SD    McNeill    25
Sea    Locklear    28
SF    Staley    25
StL    Barron    26
TB    Penn    26
Ten    Roos    26
Was    Samuels    32
Ave        26.9

Team    RT    Age
Ariz    Brown    25
Atl    Clabo    27
Balt    Oher    23
Buff    Butler    25
Car    Otah    23
Chic    Williams    24
Cin    Collins    23
Cle    St Clair    32
Dal    Columbo    30
Den    Harris    24
Det    Cherilus    25
GB    Barbre    25
Hou    Winston    25
Ind    Diem    30
Jac    Britton    21
KC    Ndukwe    27
Mia    Carey    28
Min    Loadholt    23
NE    Kaczur    30
NO    Stinchcomb    30
NYG     McKenzie    30
NYJ    Woody    31
Oak    Green    33
Phi    Andrews    28
Pit    Colon    26
SD    Clary    25
Sea    Willis    27
SF    Synder    27
StL    Goldberg    29
TB    Trueblood    26
Ten    Stewart    27
Was    Heyer    25
Ave        26.7

The average age for LTs and RTs is almost identical, so I'm not sure there's much difference, although there seems to be a few more younger LTs, which makes some sense as LT is more of an athletic position and RT is more of a size/strength position.

Taking each of the 64 ages it distributes like this:

21    1
22    1
23    6
24    8
25    12
26    5
27    8
28    5
29    3
30    6 (5 are RTs)
31    3
32    2
33    3
34    1

This seems to indicate that the most players are 25 with the major range being from 23-28.  This is definitely lower than I would have guessed.

Walker just recently turned 30, so it's not a lock by any means that he would regress as there's still many 30 year old tackles and older (15 of 64).  However, of the 6 OTs that are 30, 5 of them are RTs so that might be an indication that more athletic players are remaining at LT when they're 30+.   Walker is also an unusually large man, so it's also possible that he would be likely to regress quicker than a normal OT because of that.

I don't think this is definitely conclusive one way or the other, but I don't think that Walker's regression should have come as as much of a shock that it did.