Lee has been our best player this season by some distance and all Gers fans would have been worried when they saw him hobble off at Easter Road on Sunday.
So much of Rangers' play comes down the left hand side of the park and goes through Lee so if he doesn't make it then it will be a really big loss to the team.
Ally does have a natural replacement in Stevie Smith but, let's be honest, he is not as good as Wallace. He is a decent left-back and an experienced player, though.
It looks like goalkeeper Cammy Bell will miss the tie as well, which is another significant blow. However, Steve Simonsen has proved his worth as a back-up before and I'm sure he can step up again.
Andy Little and David Templeton are others on the doubtful list and that does leave Ally short of attacking options.
Even if their respective injuries have healed up, it will be too much to ask them to play in a game of this importance having not trained in the build-up.
Rangers are far from their strongest and Ally needs all the players he picks to play to really step up to the mark tomorrow and put in a huge performance.