I've done a quick count, just based on bare numbers (goals and assists), from the turn of the year mate
1 assist v Rotherham for Doucoure's winner, FA Cup 3rd round
2 assists v Sheff Wed, FA Cup 4th round
1 goal v Leicester, PL
1 goal v Man Utd, PL
1 assist v Liverpool, PL
1 goal v Palace, PL
If you count winning a pen as an assist (I don't, but they are now used in that 'expected threat' stat) then he got us the pen v Spurs too.
(I may have missed some but don't think I did)
Compare that to the output of our other midfielders and attackers in the same timeframe.
Come on Tim, he wasn't 'completely ineffective'. I agree in those games you say, he was poor, but again, why did we have no other way of playing? Those teams just focused on kicking him out of the game (Newcastle especially) because Ancelotti didn't have any other idea of what to do and our other players hid away.
On a technical, quality level, he is the best footballer at the club. By miles.
But in terms of importance, he's pretty much down the pecking order right now. That being said, we need more than one way of playing. So if he stays should be used accordingly.