It's the perennial problem - hiring someone who is (a) high enough quality to do the job, (b) doesn't mind sitting on the bench week-in week-out. It's especially difficult with CBs because they work best as settled pairs and chopping and changing hurts them. So we hire Pepe and play him and Vinny and end up with Nasty and Lescott on the bench. That's a recipe for losing Nasty before too long and he's really very good indeed - outplayed Vinny a lot of the time this season.
We're talking about living without Nasty for 3 games (Newcastle, Cardiff & Hull) and he should be ready post-internationals. Play Vinny & Lescott, cross your fingers and go to Boyata, Micah and Garcia if we have to. But getting Pepe in to act as back-up is an insult. Getting him in to permanently replace Nasty is wrong-headed and getting him in to rotate goes against the idea of solid pairings. I doubt whether Pepe would outperform Micah/Boyata for a dozen matches anyway.