I think Koppen has had a very solid season. The issues on the OL this year have been Light and Connolly. Mankins coming back knocks Connolly out of the starting line up. Not really sure what games you have been watching to say that Koppen has struggled and Connolly has looked good. He's been decent filling in for Mankins but he has also received help on a lot of plays especially from Koppen
Have seen this a couple of times, about how poorly Koppen is playing.. however it all seems to be conjecture, rather than reality.
It's hard to quantify individual OL play, and whenever you see a missed block, you can't really blame one person since the entire line has to communicate, and the QB should be setting the protection as well. So there will probably be a lot of disagreement on his play. But he turned 31 at the beginning of this season, and I'm more interested in the future and whether Connolly is an option. Interior O-line was considered an area where we lacked depth before the season started and I'm wondering if we might draft a center or a guard next year.
As for Koppen, he has always struggled with larger tackles. I think that's a general consensus that Reiss and many others have mentioned when discussing the Pats. But this year, Koppen has been pushed back a bit more than I can remember.
He played a real solid game against the Vikings against some very good tackles. But he really struggled at times against San Diego and Baltimore. Of course Baltimore also features Haloti Ngata who goes between end and tackle, and that'd be a tough match-up for anyone. But there were several times Koppen got pushed back, blowing up entire running plays. But Antonio Garay blew by him easily for a sack in the San Diego game.
Again, it's a hard thing to quantify, and my eyes could definitely be lying to me since you rarely see much of a center unless they screw up and a DT or blitzer runs by them to sack the QB. Football Outsiders also shows our OL as one of the better ones in the league so far, and runs up the middle are solid across the board, so it hasn't been a major weakness.
But I do wonder if Connolly is the guy to take over at some point, or whether we'll have to draft someone.