He said: "When you get a chance to play you really have to grasp it because there is such fierce competition for places.
"There is always someone capable of taking your place in the next game."
Whether the Scottish international keeps his first-team shirt against Portsmouth tomorrow is open to debate, but he has certainly made a case for being retained in the starting line-up.
Two goals against Arsenal in the last round, a rousing 4-0 win, and fine performances against Newcastle and Lyon - in the Champions League this week - have stated his case.
He said: "This situation is great for us as a club, and individually, because there are going to be a lot of games for everyone as we get down to the nitty gritty. Hopefully our squad will carry us through in all competitions."