The 26-year-old has been struggling for some time and may even have the power to make or break Steve McClaren's reign at St James' Park - already.
After eight league games, the Tyneside outfit sit rock bottom of the table - below even struggling Sunderland on goal difference.
Apart from the odd display of resilience against the likes of Arsenal, Manchester United and Manchester City - which still only produced one point between them - no one has been firing at St James' Park.
Least of all Moussa Sissoko, who underperformed last season and has taken that to a new level this term.
The 26-year-old keeps expressing his desire to play in the Champions League but, if he can't hack it at Newcastle, there is no possible reason he will do better when the stakes are higher and he will face far greater competition for a first-team place.
But Sissoko's poor form means he may just be Newcastle's most important player in the coming weeks.
Indeed, as the Magpies' talisman at his best, the midfielder can change the fortunes of the struggling side if he just shows some desire, effort and determination.
When on form, Newcastle fans have raved about Sissoko and he's played a big part in leading by example and driving his side forward.
We haven't seen that Sissoko in a long time, however. Were he to return, the St James' Park outfit's whole dynamic could change. Should he continue in his current state, though, his poor form will likely be mirrored by the rest of his side - and it could have devastating implications for Steve McClaren.