Where is Dianna Agron on Glee in the 'Quarterback' episode?

Answer 1

Dianna Agron was not in the episode "Quarterback" because she was promoting her movie with Michelle Pfeiffer and Danny DeVitto. Her schedule didn't match up with the shooting of the episode. She wanted to be on the episode, but was too busy to fit in the filming into her schedule.

Regarding rumors about a possible rift between her and other castmates:

"So I've nothing but love for that show and everybody involved in it and it was such a huge part of my life, so I think it's equally hard when I'm not there every day anymore, I don't see all of them every day anymore to have things like this fly around. It's more heartbreaking than it would be if I was there with everybody. It makes me feel even farther away from our show." - Dianna Agron