Med schools have different policies on the CSA (we were required to have TAKEN it to graduate) but it didn't have any effect on my participation in the NMRP match last year. I took it in feb (about three weeks prior to the match) and it was never an issue with regard to my ERAS or NMRP applications or during interviews. Programs may have different policies regarding completion of this exam as well...several that i applied to required you to pass the step 2 CS prior to starting your residency. Unless things have changed, i don't think the CS has any influence on your ability to participate in the match. Good luck.