As in the Southampton game, once he went out, it felt like we have no physical presence at all and Chelsea was able to get easier to our box. Granted, Chelsea started to push before he went off, but once he was substituted it felt that their control of the game became official.
The good thing about Fellaini is that he can be useful in the closing stages of a game whether we are leading or need a goal. If leading, he can help defending, especially set pieces. If we need a goal, he can be the target man. Either way, LVG sees in him a starter (at least for now) and I think rightly so.