Well I think he had an illness then got a red card.There's a reason for that...and the reason was that he's feeling all those games he hasn't been used to.
I agree on your overall point that he was a bit overused pre Christmas, but he clearly hasn't been overused in the last month. He has only started 3 of the last 6, one of which he didn't finish due to a sending off.
Its extremely disappointing, and I'm not going to defend the clubs overall record with injuries and getting players fit. But this one does just feel like a bit of horrible luck for both Jack and us.