There's no doubt Matthews hasn't performed up to his contract over the last three seasons...
I'm in agreement that he did not play up to his contract the past three years but I also believe that there are plausible reasons for that decline in his play, one of which you have already addressed above. Pardon the redundancy below. But here's my assessment of his performance over the past three years:
As you mentioned earlier, Wimm, he played out of his normal position on the outside for one full season and part of another in the two years that preceded last season. Those should have been two of his prime years playing at OLB. The team had obtained Peppers and they took full advantage of his availability, freeing Matthews to play ILB full-time. He had never played ILB before in the NFL. The so-so results speak to that and also to the glaring weakness that ILB had become for the team -- so much so that they left themselves little option but to fill ILB with their best player on defense while still in hot pursuit of the Lombardi Trophy.
The latter has to be pinned squarely on Thompson since ILB does not seem to be one of his favored "core" positions. We all know that TT has shied away from free-agency for ILB and he has not used a top pick in the draft to fill it since the A.J. Hawk acquisition -- who may have been drafted while they were still playing a 4-3 defense if memory serves me correctly. The bottom line is that Matthews took one for the team. Yet he's held in contempt for a coaching decision and a GM personnel failure. TT didn't get his money's worth for the level of play that occurred at ILB but that's on him not on Matthews. We'll never know if Matthews would have produced more impact plays had he played on the outside instead of at ILB. My guess is that he would have. He is far better suited to play OLB and the results from 2014 and 2015 should have proved that beyond any doubt.
Last season he was injured. Anyone who has ever experienced a traumatic and significant shoulder injury should be able to empathize. It's not an exaggeration to say that a person may become one-armed and that the shoulder may not heal very quickly. With my own shoulder injury I was unable to lift my arm high enough to wash or comb my hair. It took several weeks for it to heal well enough that I could resume most of the routine everyday activities without pain and loss of motion that we all take for granted, like putting something on a shelf. But by then muscle atrophy was significant and lifting weight only aggravated it and set back my recovery even further. It was and still is a delicate balancing act. Any nine year old girl could have whipped me in an arm wrestling contest for weeks if not months.
Like Matthews, I did not have mine repaired surgically. In my case it was against doctor's advice. I'm impressed that Matthews was able to play at all with that shoulder considering the injury. And, of course, there was the chronic hamstring injury to deal with. That only exacerbated his mediocre play and it may have been aggravated by compensating/favoring one shoulder, perhaps limited to being a one-trick (one side) pass rusher and set-up as a tackler.
Again, if anyone has ever experienced a significant injury to a limb or back they may also have experienced problems that were related to compensating for their original injury. Sometimes more than one body part becomes affected. Personally, I give him the benefit of the doubt because of my own injury history and the secondary health issues that occurred as a result. My pay could have been increased by 1,000% and it would not have made my shoulder feel even slightly better or caused it to heal any faster.
This is not directed at you, Wimm, but the injury issue leads to the subject of Matthews sitting out at the end of the notorious NFCCG loss against the Seahawks. Lest we forget the team was only one first down or one stop away from going to the SB and nobody else delivered. Peppers thought it was over when he strangely motioned for his DB to take a knee after the interception. Many of us also believed that we were probably just a few short minutes away from victory or our hearts would not have been so broken. The players and coaches performed as though playing out the clock was a mere formality on their way to the SB.
Matthews was purported afterwards to have "tweaked" his knee sometime during that game. That seems to be conveniently overlooked. It is highly likely that the coaches sat him down so that he would not aggravate it further with the SB game on the line only a couple of weeks later. Good plan if virtually the entire team had not wet their pants over the last few minutes. Again, Matthews is being made a scapegoat by some for that loss. By my count there were at least 22 others who could also be made scapegoats. And if last year was not proof enough that Matthews will play through injuries then there's no convincing some fans. The difference between Matthews and Sherman in that NFCCG game is that the Seahawks and Sherman were still desperately trying to win the game by coming from behind. The Packers foolishly mailed it in thinking it was in the bag.
I'm hoping that Matthews has a monster of a 2017 season.