He explained: "Benfica play football, that's their style. So, when they smother a game, they do it in a different way from others who come to Celtic Park and try to kill it by man-marking, keeping it very tight, playing three at the back, and flooding the midfield.
He said: "That's why we had to get Jan a bit of a game in midweek against Hearts and another 90 against Kilmarnock on Saturday. Everyone knows our big two at the moment.
"Now, that can change. But you don't change because someone comes in and does well in a game or two.
"Say Scott got injured next week and I put someone else in who scores a couple of goals. When Scott is fit again, do I leave him out? Or do I say to him that for all that hard work you have done for us, there is no way it can be destroyed by someone else's 90 minutes on the pitch?
"To earn that place, you have to show over a period of time you are ready to replace someone. You just can't say after one game, right that's it.
"When Jan, who is our main striker, is fit, we have to try and get him back into our side."