From what I gather from that quote, I figure that if Xavi leaves, we'd have to replace him too this window. Possible successors:
Gündogan: Unfortunately, he missed the entire last season due to injury. If he manages to reach his form prior his back injury, he'd be a subject next summer (or the summer after that because of the transfer ban). There's no way that we are going after him this summer, that'd be too big a risk.
Koke: Unrealistic. The only way he is gonna leave is if we pay his buyout clause and there's no way we are going to do that without buying a couple of CB's first. He'd be ideal though.
Thiago: Unrealistic. He is one of Pep's favourites, and he seems to love playing under him. Such a shame we let him go.
Samper: That'd be quite a bet. From what I've seen, they do have similar qualities and he is definitely one for the future. I'm not sure that he is ready yet though.