On paper, Pochettino always line up with a 4-2-3-1 when he is not using a back 3.
However, due to the fluidity of his tactics, when in possession, the formation shifted to 4-4-2 diamond.
In this attacking stance, Sissoko and Winks will pair as a pivot to spring the attack. This works well for us so far as Winks can put himself in good position to spray passes and dictate the tempo of the game. Sissoko is good at making incisive run and is hard to mark from midfield.
This formation is extremely useful against teams that likes to press high. There will be spaces in the opposition that Sissoko can exploit during transition. While Sissoko is not a finisher at all, he has lots of option in front of him, eg., Eriksen to make incisive passes/through balls, Dele Alli as a shallow striker to make runs in behind the defenders, Kane who can hold up ball, Son for his trickery and pace.
That is why we are such a force when everyone is fit and fighting. One eg., is how we demolished Dortmund. However, injuries decimated a lot of our options this season and that is why we struggled towards the end of the season. Pochettino has to improvised ways to overcome our opponents and with abit of luck and “never say die” spirit, we are in the finals!