I don't think we are even close to being a Top 5 injured team this year (see the Yankees, for instance. And we haven't lost a starting pitcher).
I also think when you have one of the best offensive starting eights in the league, losing 25% of it hurts a lot more. Last year if we'd lost Crawford (which we did) and one of the OFs (Hoskins actually did get hurt in May) it wasn't as big a deal.
But obviously having both back-ups for SS and CF getting hurt at the same time is pretty unusual.
I've lost track of who is actually on the roster/bench now. It's Gosselin, Cozens, Williams, Knapp, with Rodriguez and Altherr technically now starters. So once Segura comes back I would think Cozens stays and Gosselin goes - though Gosselin and Rodriguez are both probably more able to play CF than Cozens (in theory, if you still buy defensive spectrum).