Our midfield is possession based. This is why we do so well in Europe and against Celtic - we keep the ball, looking for an opening and making the other team work. Allied with this is the mobility of our front three, who are able to take a ball in a tight situation with usually only one man to beat. Against teams that get a nose-bleed outside of their penalty box, we don't need a midfield three of Jack, Davis and Kamara pretty much in a line, we need one of them much more advanced.
This is exacerbated when we don't have Alfie. We can just play the ball into him and see what he can do. Defoe is different. He plays on the shoulder of the defender and uses his pace. I lost count of the number of times one of our midfield three picked the ball up, then baulked at the chance to play a through ball, which is exactly the ball that Defoe wants. Even against teams that park the bus, this type of pass, albeit harder, will still work and it's the type that got us the penalty against Stranraer.
It's also why we will do better against Hearts than we did tonight.