I think he choked.
I think he was in a pressure situation where he needed to be the man in a game with big consequences (1st place in East) against our most hated rival and he just couldn't handle it.
All that time he held onto the ball, I think he panicked and in the pressure situation, he lost his field vision and he lost his accuracy and touch. The field vision is the most concerning. Anyone can have some bad mechanics for a day, but to lose the poise and vision in a day when he was not rushed much, that is a killer.
I did hear about the potential groin injury before the game started but he was said to be over it by Thursday. Anyone who has ever had groin pulls knows that if you have one, you walk funny, and if you try to run or move laterally, it is very noticeable and the gimp is more pronounced. There was only once I saw him walk a little funny back to the huddle and it was after a hard knockdown.
Up until this point in his career, he really only has had two pressure situations, IMO. First was this year in the starters competition. He uncharacteristically struggled with accuracy when it came down to the wire. Forgetting about running with the ball, he just didn't play QB well in those games. The second was Sunday. All of his starts last year were absent the pressure to win. Sure there was plenty of pressure with tat depleted OL last year, but not to win. His first start last year was for a 3-6 team with a shit load of injuries, the season over. His last start last year was for a 4-11 team.
When you have a guy who chokes, he will not be able to break it. He may come in in a no pressure situation but he won't be able to lead in a game where it is on the line. Think Kolb after the first hard hit of his career. He was skittish and never recovered. I fear Foles will be the guy who plays well occasionally in relief, but in that important high pressure game, he will never recover.
His performance was that bad to me. The fact it was against the second worst defense in the NFL worsens it.