When it comes to McCarthy, if he comes on, great. If he doesn't, great.
He's the only guy we're recruiting as a safety currently - so I don't think there is any correlation between Leslie and McCarthy. At this point, safety recruiting is either McCarthy or bust, with an asterisks by "At this point", in the case that some "out of nowhere" senior blows up.
He's good enough that we'd tack on to an already chock-full position, but he's not good enough to "save a spot" for him no matter what.
So if he's in, we have a really nice tag-team partner to pair with Harrison Smith, and can ease the transition for when the safeties from the recruiting classes of 2005 and 2006 hit the road.
If he's a no go, I certainly wouldn't mind seeing his "spot" used elsewhere. Could go as as an extra defender (5th LB?), an extra offensive scholarship (5th OL?), or even devoted towards next year.