In those vanishingly few matches per season where we have that space and if he's at the top of his game, then he doesn't stand out like the sore thumb he usually does.
On his really good days he's a "meh" performance in modern Spurs terms. Just look at the competition for his place. If he's playing in the middle then there's Dembele, Dier, Winks and Wanyama (sometimes Eriksen with the right opponent) who are all well above him in the pecking order - their average days are significantly better than Sissoko's good ones.
If he's playing further forward then it's the same story. Alli, Eriksen, Lamela, Son - they all outperform him on their off days.
