The Gunners' captain is important for Wenger, that's why Cesc is not traveling to Ukraine with the rest of the team, therefore he will miss the Champions League match against Shakhtar Donetsk.
As we know, Fabregas is still recovering from a hamstring problem, and his coach does not want to take any risks with Cesc physical condition.
"Fabregas has a good chance to play against Newcastle on the weekend, but tomorrow night is too risky" expressed Arsene Wenger. "Our captain has no real strain, just a bit of pain. But since he has had difficult injuries before, we don't want to take any risk."